Tapu Lele is a very good, if not the best revenge killer once it has a Choice Scarf and it should be used as a revenge killer in my opinion. If it has a Choice Scarf, it will outspeed even Pheromosa and KO non-focus sash variants. What's even better is that its ability eliminates priority and even Prankster which makes it even more threatening.
Tapu [email protected] Choice Scarf
252 SpA/252 Spe/4 HP
-Shadow Ball/HP Fire
Psychic is obvious for the STAB and Psychic Terrain boost. It lacks the power to 2 OHKO Chansey after Psychic Terrain but overall, I'd recommend chosing Psyshock . Moonblast is its secondary STAB and for the Dark types which are immune to Psychic/Psyshock. I recommend Focus Blast because it really needs something for Steel types. Your last choice is up to you: Shadow Ball for Alolan Marowak or HP fire for Scizor, Ferrothorn and Forretress. My choice would be HP Fire since Aegislash is banned now.
Feel free to use a Choice Specs and turn it into a Wallbreaker. I would recommend Psyshock over Psychic and HP Fire over Shadow ball in that case.