Exhaustion
Being knocked out
Electrocution

Reverting to the original personality if, say, they are far more confident when transformed. How embarrassing.

Throw on a few outfit problems...

- "secret identity", since you're going super hero the classic separation of identity between the transformed form and the regular person.... I even remember the cartoon american dragon where in one episode the main characters and his crush were both fighting and dating in the same scene because they were both hiding to each other their secret identity.

- "take my place", usually with curses, someone revert back to their normal form but only because their transformation got transfered to someone else... could also be some magic/superscience backfiring after a mistake

- "akward moment", more specific to feral/inanimate tf, when a someone revert to their normal form and someone witness their toaster/horse turning into a human/anthro (... or that time I saw a reverse tf of someone having their D*** turnign back into an anthro and apparently forgot they did that in the first place)

- "it gonna leave a mark" , having the character revert back to normal except there is still a bit of their transformed form (like a tail, or tiny patches of fur/scales or a symbol on their skin or ...)

- "force of habit", "it gonna leave a mark" but more about how the person behave , Pieck from Attack On Titan is a good exemple

- "stickign identity", similar to "it gonna leave a mark" but more if the transformed form was an entire different individual in mind

- "post tf bill", having to deal with whatever damage the transformation itself did or what they did during their transformation (Like JoGo having demolished her appart for exemple )

Time limit

Exhaustion or being knocked out

Sleep
time
something that's a comfort, like a certain food or seeing a loved one. Something that sparks a happy memory.

When bits from the change stick and you aren't completely human again.