I tried — unsuccessfully — to find the largest number of persons killed by a single falling tree.
I became interested in the subject of trees killing human beings and found the Wikipedia article "Man-eating tree":
Man-eating tree can refer to any of the various legendary carnivorous plants large enough to kill and consume a person or other large animal....Legendary. These things are not real. The largest carnivorous plant might kill a rat, but not a person. But there was a time when people could believe wild stories like this from 1874 about a human sacrifice in Madigascar:
The slender delicate palpi, with the fury of starved serpents, quivered a moment over her head, then as if instinct with demoniac intelligence fastened upon her in sudden coils round and round her neck and arms; then while her awful screams and yet more awful laughter rose wildly to be instantly strangled down again into a gurgling moan, the tendrils one after another, like great green serpents, with brutal energy and infernal rapidity, rose, retracted themselves, and wrapped her about in fold after fold, ever tightening with cruel swiftness and savage tenacity of anacondas fastening upon their prey.More stories at the link — along with a sensationalistic illustration.