There’s something I’m going to name “the Doppelganger’s Downfall” It’s that those with the ability to copy someone else always lose to the original.

I believe this is because of experience. Just because you can copy a fish else doesn’t mean you are as experienced being a fish as they are.

For that reason I say the only exceptions would be someone who lives so long they have been something longer than the real thing. Especially when it comes to powers. You may have been born with laser eyes but this shape shifter had laser eyes for 50 years and you’re only in your 20s.