Exploud is a threat indeed, but because it is so frail and slow it can be easy to take advantage of him and because he is pretty much always choice locked you can switch in to a resisting pokemon who than can deal with him. Or does exploud ohko (or twohkoes if its faster or if it can survive a hit) something with a not-very-effective move?
Edit:hmm it does beat choiceband scizor this way cause it is faster and 2hkoes with boomburst. Interesting! Aegislash wins tough from it because its slower and against aegislash shield boomburst does only 30% and aegi can 2hko in blade form or ohko if its physically attacking. Heatran can counter it as well if its locked into boomburst, but sylveon can't. It can't 2hko chansey or blissey even with focus blast so they are counters too cause they can shrug off the damage. Sitrus berry special defense milotic can counter it too but they often do not run that of course.
So certainly a threat but predictable and it dies against all sash users like mamoswine 1v1 cause it is so slow. And mega gengar koes with focus blast. Blaziken of course destroys it.
Chansey and Blissey are very rare in BSS, and Milotic, well...that's barely a thing. Aegi is a problem, but it can't really switch in, and takes a beating even from BB, though Exploud won't win against Aegi that get a free switch in if it is locked into BB. Focus Blast on Gengar is pretty rare, and Exploud lives a Sludge Bomb and OHKOs w/ BB. It's also important to note that Exploud gets a free switch in on Substitute, WoW, and Shadow Ball, though only the latter can really be predicted. Sash users are just gross, Exploud doesn't handle them at all and the only predictable sasher is Breloom. Blaziken is brutal to Exploud, but I always use at least a couple things that destroy Blazike, so even though I lose a lot, you'll rarely see me lose to Blaziken. That's an example of the kind of team support Exploud requires-something to counter Blaziken. Other team support that Exploud appreciates include paralysis support and a Pokemon w/ priority, to revenge Sashers that sneak up on Exploud. Exploud is also a good Pokemon for TR, but watch out for Conkeldurr. Exploud is fairly predictable, but not extremely so. It's movepool is quite expansive, though unfortunately that's more on the physical side(Exploud's attacking stats are equal, but its best move is special, so it favors being a special attacker over going mixed. Still, there are some other options like an LO set w/ Icy Wind, which could maybe take care of a few Sashers(Garchomp at the very least.) Exploud also greatly appreciates Baton Pass support, synergizing well w/ Espeon and Scolipede, and liking both Calm Mind and Iron a Defense boosts passed to it(as well as speed from Scoli, ofc.) A dedicated baton pass receiver should probably have a LO. As for other sets, the only thing I can think of is Choice Scarf, but that doesn't seem very good.
Exploud is far from perfect, thanks to a fairly low speed stat and somewhat poor bulk all around, but it can tear teams apart w/ the right support and its power, and can 1v1 a lot of popular Pokemon(Garchomp, Talonflame, Mega Gengar, Megamence, Landog, Cresselia, Porygon2, (Mega) Scizor, Mega Kang, Ferrothorn, and some others,) provided that they're not sashed, not boosted, and Exploud isn't locked into to a bad move or in KO range. I guess given all that Exploud should be ranked C. It is good in the BSS metagame, but it has a couple problems and competes for a team slot w/ other Pokemon weak to fighting, since they synergizes poorly w/ it and thus shouldn't be run together.
EDIT: Anyone else notice the Sprite for Serperior got replaced w/ Chansey?