German perspective, I don't know what is applicable to the US and other countries.

First and foremost: Removing sales tax on (basic) food. Sales tax in general hits the low income population much harder than any other tax. Lowering income tax when your income is low or non existent doesn't help as much as just to not pay an additional 7-19% on bread, milk, eggs, legumes, fruit, vegetables.

Build more affordable housing and capping rent pricing.

Increase social security and unemployment to boost the economy. Poor people don't save up. What they get they spend. Every 1€ they get will immediately go back into the economy, hence creating economic growth, which then will create more jobs that need to be filled. The stupidest thing one can do in times of crises when people are unemployed is to save to push them into non existent jobs. If jobs and income make people richer, then you have to provide jobs to begin with. A saving instead of spending economic mindset of the public is the worst thing you can do there, and this especially regards government payouts to low/no income individuals. Or, you know, invest in people.

Inheritance tax. Raise the limit of tax free inheritance, but after that limit is reached, tax much, much more. Nobody cares if you inherit a 2M € mansion. Hell make it a 10M mansion. These aren't the inheritances we should be worrying about, and making sure everybody knows it is not about their family's house being taxed away from them will hopefully increase support for inheritance tax.

Capping wealth. 100% taxation over a certain amount. If you can't make more money, why steal wages from your employees or raise prices more than it's needed? And if you do, all extra money will be taxed and gets back to the people anyways.

Universal Basic Income for people who are below an particular netwoth with it gradually decreasing until they get none.

Change the goal. The French economist Thomas Piketty (https://en.wikipedia.org/wiki/Thomas_Piketty) has demonstrated, using 250 years of historical data, that the wealth gap increases as long as the rate of return on capital is greater than the growth rate. Every institution in the western world (including governments who are trying to maximize tax income) are trying to maximize return on capital. Growth is good if it is in the public interest. If we only want growth because it increases our returns on capital, inequality is the result.

Reset minimum wage to an actual living wage, with mandatory cost-of-living increases each year.

If a corporation has workers on public benefits (food stamps, whatever), then that corporation is fined twice the amount of public benefits each employee receives. If an employee working two or more jobs is on public benefits, then each company is fined twice the amount that employee receives.

Firm up Unions and Union protections.

Limit the amount of total compensation anyone involved in a company - including the entire C-suite and Board of Directors - can receive to, say, twenty times the lowest-paid employee. "Total compensation" to include stock options, bonuses, travel and business perks, etc. Also ban companies from employing / hiring / chartering private jets; if the C-suite wants them, they can pay for them themselves.

Semi-related to above, but not directly related to your question: For company travel, ban companies from sticking their employees in cattle class (whether travel, hotels, meals, etc). Nationwide mandatory rest and water breaks for all outside work (none of this bullshit where agricultural workers in Florida don't have water breaks). Mandatory rest and food breaks at work, with none of this bullshit where the break starts when you leave the line and it takes you ten minutes to get to the lunchroom and ten minutes to walk back. Mandatory sick time for all employees, mandatory vacation time for all employees. Hold companies that out-source work liable for the treatment of the out-sourced workers (none of these "well, those are independently contracted workers, so they set their own schedule even if we've given them unrealistic goals and will penalize them for failing to meet those goals".)

Overturn that law that says companies and corporations have a duty to consider the "rights" of the shareholders (which is where at least some of this "line must go up" shit comes from).

Ban private equity and similar types of predatory businesses / people from investing in human needs. That includes housing; water, sewer, electric, gas, communications and similar utilities; food production; whatever else is essential for people to live half-decent lives.

Actually and aggressively enforce wage theft laws, with employees getting multiples of their deserved payouts, company owners and directors facing personal fines and prison time, and the corporate death penalty for any companies deliberately or systemically engaging in wage theft.

If you're going to continue to arrest workers who are in the country illegally, arrest, prosecute, fine and jail the owners, C-suite, and managers of companies that employ undocumented workers.

If you retire and your income is over 100 times the federal poverty rate (which currently means an annual income of about $1,200,000), you don't get Social Security income, and use that money to increase benefits for people on the lowest level of the Social Security ladder. In a similar note, allow people on disability, Medicaid, etc, to have more than $2000 in assets before they start losing benefits. $2000 in assets was nice when it was set in the 1980's, but I don't think it's been raised since, and $2000 isn't much in today's economy. Similarly, the max-assets limit should get an annual cost-of-living increase.

No one "needs" more than two homes. If you (or you and your combined shell companies, it you and your family, or whatever other ways you find to get around this) have two or more homes, you personally have to live in that home for at least 90 days each year, with similar aggressive reporting requirements as inflicted on people who get Medicaid, food stamps or other public benefits. Failure to live in the home or meet reporting requirements means you have to pay some decent percentage [maybe 25%] of the home's current value to the [state? local?] government. If you fail to meet the "actually live here" requirement for a certain number of years (say, 10 years), your home can be auctioned off.

Limit the number of living units an individual landlord / company / corporation can own, run, or otherwise profit from. Limit rent to a certain percentage of the unit's same value, plus a maintenance/repair fund, plus some reasonable amount of income.

Heavily tax income over a certain amount. Tax wealth over a certain amount. Tax estates and inheritances over a certain amount.

Go over existing laws and start closing so-called "loopholes". Those "loopholes" aren't accidental wording in the law that people/companies discovered and decided to take advantage of; that was wording that was deliberately added to the law, at the behest and bribes of corporations and wealthy people, so they could intentionally avoid the law.

Probably a bunch of other shit, but this is a semi-decent start.

Inequality is always going to be prevalent in a meritocracy. And that's okay. It should be possible to just get by nowadays and if you want a little extra, you can work or invest what you already have. A Universal Basic Income paid for by a wealth tax would work. There are of course also other means of financing UBI. Heavier taxing of luxury products, air travel, mileage taxing for cars, there are tons of options. Sadly none of these will ever be applied because countries are usually run by people who would feel these measures themselves and it would prevent them from putting spinning rims on gold jetskis.

Trickle down economy has been tried, but its positive impact is doubtful.

A constitution that makes the government bound to improving the welfare of its citizens. “All laws shall have the intention of improving the livelihood of the bottom 35%” would be a place to start.

“It shall be illegal to or provide healthcare that is reasonable and affordable for all citizens.”

“It shall be illegal to fail to provide housing for all.”

You know, basic stuff a government should be doing.

Communism

A real, functional minimum wage across all jobs (close the loopholes around tips, piecemeal work, etc). Have it pegged to inflation so it stays a living wage.

Direct government support for and Incentivization of worker Co-ops across the supply chain, and specifically for digital infrastructure.

Worker owned and run businesses distribute wealth to the working class directly, and digital infrastructure like datacenters and fiber optic networks which yield strong ongoing revenue in exchange for intensive uo-front work on planning and cinstruction followed by ongoing preventative maintenance are an ideal target for co-oping if a lender would specifically support it. The lender of choice could easily be a government agency, with ag loans, innovation loans, and the SBA in the US all as examples of how this can work.

Similarly alternative energy supply chain can and should be co-op, not just as consumer co-ops like there are in rural power utilities, but worker co-ops as construction and maintenance contractors for the solar and wind fields and power grids, as well as the hardware manufacturing facilities.

Direct revenue-driven worker ownership is the surest way to increase economic equality, as direct share of revenue and worker-member units are resistant to the speculative value manipulation that drives most wealth accumulation at the top in the "public/private" corporation model of neoliberal capitalism.

Make it illegal. Say 10x more then the median is a jail scentence of 10 years.

There is noting more economically toxic then inequality.

Social assistance, labour unions, funding for infrastructure, free healthcare and education.

The American President Franklin Roosevelt, who was elected during the depression, and his New Deal policies were credited with pulling millions out of poverty, expanding the middle class, increasing standards of living, and rebooting the economy.

The New Deal led to the creation of the SEC (securities and exchance commission) to protect investors from shady stock market practices and the FDIC (federal deposit insurance corporation) to protect people in case a bank fails. It increased public works funding which in turn created jobs and better infrastructure. It also created welfare programs to get people out of poverty and labour unions.

The increasing wealth gap in the United States can be tracked to the slow rollback of these policies and reduced funding for the measures put in place. In the 1980's, Reagan took the opposite approach with trickle down economics that cut funding to social programs and lowered taxes rates at the top brackets.

Now, the New Deal wasn't perfect, it left a lot of people behind, but the spirit of it goes to show how economic controls and social supports are integral to a healthy population and economy. Inversely, Reaganomics led to the 1987 stock market crash, higher unemployment, and higher income disparity.

Land Value Tax