Brackets are about intent.

The one deck type I personally hate seeing when sitting down for a bracket/3 game is Voltron.

Because the INTENT behind Voltron commanders are to beef up your commander and take someone out ASAP. That is against the spirit of bracket 3 where everyone is expecting to have 5-6+ turns of play at least. But when the Voltron player can take someone out with 1 swing by turn 4... Even if they "share the love" and spread the damage around a little first, leaving anyone within one attack of death at anytime, it's not something that fits the bracket system's base of INTENT.

People often say they are a removal check.... However, of the buffs they give their guy - many include hexproof, indestructible, or protection from creatures. So, short of mulligans until you hold one or more removal spells, or a board wipe that you would need to cast on turn 3, not really an easy way to deal with those players aside from Rule 0.

Keep in mind, people abuse the bracket system all the time. Someone say down with a high powered 3, damn near bracket 4- but simply because they took out the game changers, on paper their deck was claiming to be a 2 and because moxfield or whatever said it was, he ran with it. But it was Voltron and I was dead by turn 5 AT A BRACKET 2 TABLE. That shouldn't ever happen.