Hitler
Hitler the Otaku - picture by Evang-y1203
Hitler tends to be a very stable meme once introduced to The Sentence Game due to his characteristic mustache and swastika, and his wide acceptance as one of the most evil characters in human history tends to result in him being placed in humorous or amusing situations. Hitler was the head of the Nazi Party, Nazis also cropping up on TSG quite often.
On the other hand, his association with genocide can also result in him appearing in any game featuring death, destruction, or piles of stick figure bodies. As far as ultimate evils go, Hitler has only appeared in a few games less than Satan at the moment.
Many Hitler variations show up, some common ones being Hitlerduck and Spider Hitler.
Examples of Hitler games: