Find a Lemmy app that has user tagging (I use Voyager, and previously Connect) and when you see these users make a note of each one with a red tag so they stand out when you're browsing.

You'll start to see the bastards turning up in all kinds of conversations as well as posting ridiculous shit. That's what I did with the Russian/American trolls/bots during the american election. Very enlightening to see in a political thread who the repeat offender shit-disturbers are so you can down vote, argue with, or report them instead of blocking them and allowing their infection to spread.

Tagging is handy for nice people as well; the community of people around you on Lemmy starts to look more familiar, smaller, and friendlier than you realize, and dick heads become easier to spot.