Otto's first act after going Fake Defector in "Meet the Wigglenog" is to make everyone stop having to bounce all over the walls...by shutting down the Super Robot, which the nog in question had just set on a new course in order to begin a reign of conquest. While this obviously wouldn't have done much and more likely actually was specifically intended to make everyone stop getting bounced everywhere, it could still be seen as a hint as to his actual intentions.
When Captain Shuggazoom left the Alchemist's home, he was already transforming into Skeleton King. And the 'Hyperforce', just normal monkeys by then, were witnesses how his body slowly degraded, before he changed them into cyborgs and erased their memories. Could they have fled should the Alchemist have become violent towards them? WAS he once or sometimes, when Skeleton King realized the Alchemist would want to make them into a force capable of opposing him? We don't know and that is the most terrifying about this time.
The episode "Galactic Smash" centers around a game where players destroy inhabited planets to score points. One player, The Commodore, sets his sights on Shuggazoom, with predictable results. The problem is that there's at least 4 other players on the scoreboard, all of them with the same goal, so even if The Commodore is dead, there's at least 4 others going around the universe, doing much the same thing.
There's definitely more than 4. When bragging about destroying Aliana's home world, The Commodore brags it "put him in the Top 5." The only way that could work is if there was more than just the 5 people playing.
Early on in the series, the Monkeys suck as guardians. They may love Chiro but "Pit of Doom"'s main conflict came about because they failed to, in the words of the reviewer Netbug, "protect their pet human" and because they decided that leaving him unsupervised when he was already upset, which is clearly affecting his ability to be rational, is the best course of action. This could have gotten Chiro killed if Skeleton King had decided having the boy out of the way permanently was more useful to him than forcing the Monkeys to surrender.
When Chiro brings out Mandarin's glove in "The Sixth Monkey", the team's general reaction is fear, which given Mandarin's betrayal and personality, makes sense. But Otto's reaction? He goes into full-on Troubled Fetal Position. What the hell did Mandarin do to him? I mean he tried to freeze Nova to death as part of a "training exercise" and she doesn't melt down at the idea of him.
Might veer more towards Fridge Sadness if Mandarin's comment about Otto once being his "closest ally" bears any weight. It could have been less of a fear response and more one of emotional anguish.