Shell Smash

Shell Smash has long been regarded as a healthy aspect of the BH metagame with several aspects of counterplay, but in Gen 8 it was banned due to being just too explosive and diverse. Though the metagames are different, these arguments are also functional for Gen 7. Smash is primarily used by Mega Mewtwo X, Mega Gengar, and Red Orb Groudon, but others such as Primal Kyogre, Regigigas, Arceus, Necrozma-Dusk-Mane, and all the legendary dragons can make great use of it as well. Slower and more reactive teams reliant on Pokemon like Specs -ate users practically get pushed out of the meta by Shell Smash offense because they're unable to trade down against these teams to secure a favorable endgame, although these teams already have other issues.

One issue with Shell Smash as a move is that it's not easy to click. Even with Prank DBond or Sash Spectral in the back, hyper offense teams still get owned by opposing Spectral Thief or specific Prankster users like Giratina. The strategy has seen a lack of consistency and some describe it as "high risk, high reward" and therefore healthy. Additionally, there are quite a variety of healthy Shell Smash users, so one might also look to the other controversial aspects in the meta and point to them instead.

Important Links:
Smash Discussion in BH Suspect Thread: https://www.smogon.com/forums/threads/balanced-hackmons-suspects-and-bans-thread.3588586/post-8216624
Modern Shell Smash Replay: https://replay.pokemonshowdown.com/gen7balancedhackmons-1252023622
Example of a "slower" Smash team: https://pokepast.es/eaf2295d813f893f
BMOC: https://pokepast.es/bdf77a2c6ff7004e