For a character:
What is is a good limitation for Subjective Reality so that someone fighting them could stand a chance?
They could only be able to make a certain number of changes in a period of time. Rendering them pretty much powerless for a period of time, unless they have other powers.
They could start out only being able to make minute changes, and will only get stronger by using subjective reality more and more.
Any changes could be temporary, with reality restoring itself after a certain amount of time.
Sheer conviction can prevent it from being used on people directly.
If not controlled correctly or messed up in some way, you could get some Spider-Man Into the Spiderverse end scene stuff, and the person could lose total control.
Have a form that they turn into to distort reality but it takes a lot of energy or it hurts them to turn into it
What do you think?