Analysis work

Shark Attack is just a cute term that is really masking Garchomps actual effectiveness with its more effective set in the Bulky Chomp variant. The damage on physical contact users that Garchomp can procure gives M-Sharpedo increased sweeping opportunities late-game and it should be emphasized that this utility of Rough Skin along with Stealth Rock and the ability to phase out with Dragon Tail will go a long way in helping M-Sharpedo.

The combo rocky helmet + rough skin to Garchomp Bulky Defensive helps sharpedo a lot, because physical attackers like landorus T are being worn down really easily

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Magnezone pretty much helps with Ferrothorn and M-Scizor mostly. All the other steel types in the tier do not want to be taking Strong Jaw boosted Crunch at all so this aspect of Magnezone needs to be a bit more specific since it's really a luxury partner in all honesty.

Magnezone is the best partner for Mega Sharpedo, he can trap and kill steel types that can beat Sharpedo.
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You only named two users of spike hazards with one of them being almost foreign in the tier so this needs a lot more in there such as some of the Spike users I previously mentioned.

Spikes and Toxic Spikes are welcome as well along with any residual damage. Spikes provides more damage for Mega Sharpedo to abuse, and Toxic Spikes allows it to abuse Protect for chip damage. Scolipede makes an excellent lead since he can use both Spikes/Toxic Spikes. It encourages your opponent from leading with a priority user such as Talon flame while you can kill it with Rock Slide or weaken it with Endeavor assuming you're running Focus Sash. Against non- Priority Users teams it can just spam the crap outta both hazards, Tentacruel can be played as a Toxic Spikes setter if your team is oriented balance or bulky offense as he has a correct bulk. He can also spin Entry Hazard and absorb Toxic Spikes due to his poison type.
Spikes User like Skarmory and Klefki can have the same role as Scolipede in HO team, Skarmory can be played Custap Berry and spam spikes, Klefki can also spam spikes and runs dual screen, as tentacruel, they are bulky, so they can be played in balance or bulky offense team. Ferrothorn can also come in a balance team for the same reason
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Team options really just needs to be beefed up with actual stuff that provides synergy and not stuff like Bisharp and Breloom that is described in a way where you're just making M-Sharpedos end game worse.

No need j'ai refait le Team Option avec toi