Toph's Earth-bending
I figured Toph’s earth-bending was one of the strongest because she was blind.
Hear me out.
If you lose one of your five senses, at least one of the others will rise to compensate. That's why blind people tend to hear better.
But Toph's hearing didn’t increase. Her sense of touch did. Her earth-bending was so powerful because it was her eyes, her sight. Why hear better when you can feel exactly where things are without even touching them?
It’s also why she feels nervous in water or air. She’s not on the ground. Her earth-bending is compromised. She can only feel what’s touching her. It scares her. She clings because she’s only truly blind off the ground.
But all in all, it’s an amazing example of being empowered by a disability.