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 moves which makes it even more threatening.
Tapu Lele @ Choice Scarf
Ability: Psychic Surge
EVs: 252 SpA / 252 Spe / 4 HP
- Psychic / Psyshock
- Focus Blast
- Shadow Ball / HP Fire
Psychic is obvious for the STAB and Psychic Terrain boost. It lacks the power to 2HKO Chansey after Psychic Terrain but overall, I'd recommend choosing 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.