10. Getting His Body Stolen From Him - Superior Spider-Man
Though we all love seeing Otto Octavius run around trying to do good in Spider-Man's body, the Superior Spider-Man series tends to mostly ignore one very crucial thing: that part of Peter Parker is still trapped in said body, and that Otto is a huge monster for trapping the dude in the passenger seat of his mind.
After technically killing Peter by having the two swap bodies as the Doc's frail old form began to die, Otto would go on to realise that some of the plucky hero was still left in his own arachnid body. However, Peter was unable to do anything other than talk to Octavius, and was generally completely ignored even then.
This goes on well into when Otto is considered a legitimate superhero by his own right, which is completely messed up, because the man had essentially been keeping a secret hostage the whole time.