Reddit, what's the largest living animal that a human could theoretically kill with only his bare hands?

In the most optimal scenario, I'm thinking a giraffe, maybe? A stretch, for sure, but not outside the realm of possibility. The strategy could be as follows: hide up in a tree, wait for giraffe to pass by, leap onto giraffe's head and grabbing onto its horns (conveniently shaped like handles), while choking it to death with your legs.

Can someone top that scenario?

Rules are as follows: 1) human must survive the encounter, 2) must take place within an 18 hour window of the human's choosing. 3) the encounter must occur within animal's natural habitat.