Keep it mind that the move will be exclusively available to said Pokemon (and exception being probably Smeargle with Sketch), so you can tailor it to the Pokemon's need despite the move being possibly broken everywhere else
Farfetch'd F'ntastick [Physical. 90 BP, high chance of landing a critical hit. Flying]
The moves need not necessary make the Pokemon high OU or even Uber, just as long as it gives the Pokemon a niche and actually make it useful for the case of otherwise hopeless Pokemon. So feel free to give one to Salamence without breaking it as far as possible
How does it help Kangaskhan actually? I was thinking Flareon needs a physical stab priority because of lol movepool and speed, whereas Farfetch'd at least gets a damaging move when doubled with Stick (hence the move name) to critical hit. Granted, only Flareon would get a lil bit of improvement while Farfetch'd remains arguably unusable
Gardevoir: Black Hole: 5PP --- Power --- Accuracy Dark Type. Opens a small black hole that absorbs move damage, giving Gardevoir a +3 Def and Sp.Def boost for 5 turns. I was thinking of making some completely broken OHKO move, but you said no broken moves, so yeah. This move is supposed to cover Gardevoir's rather decent bulk.