Pennywise kills a handful of people every 27 years and has been doing so for 300 years or so. He probably has kill count under 100.
Between the kills he gets that are directly shown on screen and the number of casualties you could reasonably assume were the result of his actions, Heath Ledger’s Joker probably killed a few thousand people.
Ronald McDonald on the other hand, was the main marketing vehicle for a company that sells food products that are incredibly unhealthy and addictive. He is probably indirectly responsible for the deaths of millions of people.
Heart disease kills several orders of magnitude more people than extradimensional demons or psychopathic clowns.