The following Pokemon take 120 base damage from Low Kick:
Snorlax
Aggron
Registeel
Rhyperior
Cobalion
Virizion
Bronzong, take 100
Actually there are more, but these are ones you should worry abut in UU
Low Kick's point is to hit the rocks and steels that resist your STAB, and those types are pretty heavy, giving you a powerful low kick more often than not, and it will get powered up by technican when the power is low enough