I dunno alexwolf, I can't see Breloom being S Rank. As in, if anything faster that is resistant to Mach Punch is still alive and healthy, Breloom will seriously struggle to sweep. Are you going to switch these Mach Punch resists in on Spore? Hell no, that's beyond stupidity. Unless your name is Xatu, that is.
Let's look at what's in S rank already. Well, the only true sweeper there is Terrakion. Terrakion has much greater dual-STAB coverage than Breloom (have I mentioned how terrible Grass/Fighting coverage is?). Can anything switch in on Terrakion? I mean stuff that's relevant, so no Golurk. Anyway, the answer to that is no. On the other hand, looking at Breloom, a ton of crap can switch in given that Sleep Clause is activated, as in most Pokemon that resist both of its STAB moves, which is really a lot. There are two foolproof revenge killers to Terrakion: Scizor and Breloom. On the other hand, if you're faster than Breloom and resistant/immune to Mach Punch (or even just bulky enough to take one), odds are you can revenge kill it. These Pokemon resistant/immune to Mach Punch are so commonplace that teams often have at least two of them by default. So, Breloom S-rank? I don't think so.
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