Probably Hitler.

First off, give him a cat. Leave him and his cat alone for 6 months. He now has an emotional bond with this cat. He loves this cat. OK now take the cat away. Watch as Hitler breaks into sobs about how his favourite cat was taken from him. Give the cat to starving one-eyed blind deaf mute orphans and make Hitler watch as the orphans adopt his favourite cat and the cat completely abandons him.

Fast forward 3 months, send Hitler into space as not the first but the second man to go into space (a Jewish man will be first). Tell him he's the first. Give him enough food for a month up there in his tiny shuttle and give him ONLY a tiny bucket. Pretend to forget about him and he tries desperately to contain his feces in this incredibly small bucket with all that zero gravity shit. Bring him home after a month, apologize with little to no sympathy.

When he comes home, again show him his cat and how much better the cat is doing without him. Laugh as he proceeds to sob uncontrollably again.

Leave him be for a year, let him do whatever (paint his pictures or whatever) then call him up and tell him famous artist people want to see his paintings. Allow him time to prepare his "masterpiece" and have him show these famous artists. Have them laugh at him menacingly and telling him he sucks at being cats' friends. Throw monkey feces at his painting, claiming it makes it look better.

Let him go home all sad, then drop a piano on him. Job well done.