Am Having a deformity in my animations

Hello everyone so i am retargeting some animations from anime sets i bought from epic marketplace and from some free characters there but when i retargeting it and apply it to humanoid rig and i set all my bones to skeleton only pelvis to animation scale when i retarget it my character arms and hands are out of place and not doing a good job i attached a pic down below pls check it out

Could be loads of things.
bad retargeting.
bad mesh weight paint.
Bad mesh skeletal structure.
Bad animation set that only works with the original mesh.

Its nearly impoissible for us to say with certainty what it may be.

To test, start with retargeting the epic skeleton to it.
if he doesn’t deform the same way, then the animation is fine and the other 3 issues are what you should look into

Next thing to test would be the retargeting base poses. And after that you would need to deconstruct the model and check on the weight paint.

Looks like you have some stray bones in your underarms that your vertices are weighted to.