Death of the Doom Patrol. 3 segments; Robotman mentions utterly defeating "Mr. 104,"
but when last seen in #106 this villain was called "Mr. 103," and he got away scot free. In his next appearance, Teen Titans Spotlight (1986
series) #9, he explains to Robotman how he had managed to survive their last encounter, which an editor's note identified as being in DP #106!
Sometime between #106 and #121, an untold fight between the original Doom Patrol and Mr. 103, now calling himself Mr. 104, must have occurred.