(Amazing Spider-Man #11, Apr. 1964 - Stan Lee, Steve Ditko)
So Otto's grand return is kind of convoluted, and kind of slots him into a role where any returning villain probably would've fit. It's honestly more about the ongoing Peter/Betty Brant romantic storyline, which I haven't commented on at all because it's not very interesting and I know how quickly it becomes irrelevant.
Betty's dark secrets that have previously been hinted at are revealed this issue. Basically, her brother back in Philadelphia owes some major gambling debts to a mob guy named Blackie Gaxton, and to repay his debts he's arranging for Doc Ock to break the mob guy out of jail. Betty is in on this because she dropped out of school and took her job at the Bugle so that she could try and help her brother get out of debt. Otto agrees because he's being paid a lot and that'll help kickstart his new career in crime. It's a lot.
Blackie Gaxton. Terrible name. Great face, though. Please appreciate it now, because he's never appearing in another issue.