LOL you guys are too much
hahaha i miss you tim
and mewtwo isn't top tier, only vman's mewtwo is (freakin up-b edge cancel shadow claws into some sort of death combo that i can't even see cuz it's too fast)
hmmmmm.... against luigi? i suprisingly have a bit of luigi experience lol
honestly, there's not too much you can combo with... the most reliable combo is just neutral - up smash.
but against luigi, what I love to do is jump strait at him, then waveland back. normally he'll wave dash forward and downsmash/f-tilt/something else lol. but you can punish him... if you get him in the air, pretty much the only thing he can do is neutral
if he's in the air, if you jump, pretending like you're going to attack, he'll immediately neutral (at least, that's what the luigi's i fight do). if you just bait him into doing a neutral while he's falling, you can punish him easily, since it has so much lag.
usually, comboing luigi isn't the best idea, since he can pretty much break out of all of them... instead, i just like to fake approach him then punish him, and repeat. also, if you're not sure what he's going to do, a forward tilt can pretty much stop all of his approaches. f-tilt is your friend lol