First post!
I love using M-Banette in teams, it's got a great design & an amazing Attack stat, but it does suffer from possibly the worst 4MSS in the meta right now. The best way to alleviate that is to cater the 4 moves to exactly what your team is lacking, but frankly if you aren't using it for the priority Destiny Bond, just use Sableye & let something else more useful be the Mega. I've tried an attacking set, a full support set & a mix of the two, & I feel like the best set for M-Banette is attack/status/Protect/DB. As alluded to before, the attacking set just doesn't have the coverage to be an effective sweeper. Outside of Ghost & Dark, the only physical coverage it gets is Return/Facade, & Gunk Shot. It gets some coverage on the special side but who the hell's using base 93 over 165? If you're trying to use this as an all-out attacker, you might as well go with another Mega. I feel this Attacking M-Banette will only really work in RU this gen.
Frankly, the only reason to use M-Banette is for the priority Destiny Bond, but once you realise that, it's actually incredibly effective at taking down a huge threat to your team even in OU. These are the two sets that have worked for me:
Banette @ Banettite
Ability: Frisk
EVs: 252 HP / 4 Def / 252 SDef
Sassy Nature
IVs: 0 SAtk / 0 Spd
- Shadow Claw / Knock Off / Pursuit
- Will-O-Wisp
- Protect
- Destiny Bond
This is a defensive M-Banette designed to cripple Physical attackers. The Nature & EVs make it Specially defensive, with Will-O-Wisp patching up the Physical defense. Always Protect first turn to ensure you get Prankster. WoW if necessary, otherwise Destiny Bond. The 0 Speed IVs are so that after you DB, Shadow Claw hits as slow as possible to ensure the 2 turns of DB. Sometimes I ran Knock Off instead for the great utility that move gives you. Occasionally I ran Pursuit too because it was very unexpected, & didn't screw with DB because if they were switching, Pursuit would hit hard & I wouldn't be hit myself. If they didn't switch, I still had the 2 turns of DB. For that reason, I didn't want to use any of the attacking priority moves Banette gets (Sucker Punch & Shadow Sneak). I didn't need to invest in Attack because invested I hit as hard as LO Banette so Shadow Claw still does good damage. It's main use is taking down a big threat to allow your sweepers to clean up. It's not going to be the MVP every game, but it can clear a path for your own win condition to be the MVP. The mindgames with the slow DB can really take momentum away from your opponent.
The other set that I ran was:
Banette @ Banettite
Ability: Frisk
EVs: 252 HP / 252 Def / 4 SDef
Relaxed Nature
IVs: 0 SAtk / 0 Spd
- Knock Off / Shadow Claw
- Disable
- Protect
- Destiny Bond
This set turned out to be very effective at crippling Choicers. I made this one Physically defensive to deal better with Knock Off which is everywhere this gen. The main idea is to switch in on a Choiced opponent you feel Banette can take a hit from (or even better if you get a free switch that they switch in their Choicer on), Frisk is used over Insomnia so you can scout to make sure it is Choiced, Mega Evolve & Protect on the first turn to activate Prankster, then Prankster Disable on the next turn to cripple them, then you can double switch & gain the momentum back. I preferred running Knock Off over Shadow Claw on this set because if you switch in on something that will force a switch, you can Knock Off on whatever switches into you, which I found was mroe useful than a STAB that was not always reliable. The only thing you have to watch out for is if they switch in their Choicer on your Knock Off, you do lose the ability to cripple it with Disable, but not many opponents did that because they weren't expecting the Knock Off to lose their Choice item, or the Disable to stop them from using the move they're locked into. You can free switch it in later, then use the DB + slow attack combo to ensure you take something else out. This set does require a fair amount of prediction, but if you get it right it can mess with the other team a lot. I like to play high risk high reward, so this set is something I loved using, & I ended up being pretty surprised as just how well it worked.
So yeah that's my two cents on M-Banette. I do feel like M-Banette's tier will be RU this gen (Prankster activating on the first turn would have bumped it up to at least UU if not OU), but there's no reason why it can't be used in OU with good effect. The two sets I've posted are just two ways that I got it to work well.