"that fateful day, the one day those wretched galatics messed with me...
experimenting... torture... and one guard who unlike the others, was nice to me, led to my split personality... one side, my purer self, reigned over this form and my original... the darker, more primitive side, controlled my rage-induced form... the very one that almost stopped team galatic's plans permently"

main differences from slender form:
meant for combat, high stats overall, fur doesnt shine, skin acts like armor.
movelist
metal claw
force palm
-arm thrust
V
-Aura Sphere

no anthro shown here, but a fiercer looking lucario none the less.
and that's crystaline teeth shown!
unlike the slender form's gold aura, combat form shows up silver.
slight musclechub here. "original" refers to the slender form.