She's stronger than Shang and the other men. Next Pocahontas, maybe.

When she went to her grotto she was able to move that big rock covering the entrance also in "Ariel's beginning" she lifted than threw a heavy rock to free Sebastian in prison. Aren't things supposed to be heaveier in the water?

Also another scene when she climbed on Eric's ship with her bare arms

And in the original movie when Ursula was giant she blasted Ariel off a rock and Ariel fell right down in the bottom of the ocean floor between the whirlpool? No human can survive that fall.

Ariel's either got super human strength in mermaid form, or being related to a God (I heard in Greek mythology, Triton is the some how related to Poisidon therefore Ariel is descended from Gods) she's got super stregth, or just that ridiculously strong

She is certainly mentally the strongest - the physically strongest is surely Mulan, since she is the only one trained, but Rapunzel is strong enough to hold Mother Gothel and later Flynn when they are hanging at her hair. That's pretty strong.

Or Pocahontas.

Honestly I think she would be able to do the exact same things Mulan did & WITHOUT any training.

Emotionally strongest, Cinderella.

Pocahontas indeed! Then Mulan and Jasmine. And maybe also Ariel cuz she's really brave, and when u're brave u are strong! ;) It's the inside!

then Mulan and Rapunzel

Same as BelleAnastasia :)

Mulan and pocahodas

she looks very muscular.

DUHHHH.

She used to live in wilderness. She rows a boat, runs... Although Mulan is trained, she is new to it.

Pocahontas is also emotionally strong, seeing her lover away with injury.