In all seriousness I feel like the common answers I saw of Diogenes (because that was like, his entire shtick) or Socrates (because they killed him for being annoying) are probably better answers but saying its Trotsky on a leftist forum is way funnier.
He did some genuinely intelligent things during the revolution. It’s a shame the power struggle and his theories turned out the way it did, the movement he left behind, as you say, is incredibly annoying.