I certainly do agree with Azumarill for B-Rank. As a competent Azumarill user, I'm going to give in here. Azu has a very high Attack stat, and with CB, it can hit decently hard with its Water STAB. It also has Double-Edge and Ice Punch, so Ice Punch can catch the incoming Roserade or Shaymin and OHKO them. Double-Edge does reasonable damage to some bulky Waters bar Slowbro and Qwilfish. Of course Azu has counters, I mean other powerhouses like Bisharp, Mienshao, Chandelure, Scrafty, and Zapdos do too! Azumarill also stands out from Kingdra with its ability to hit hard right off the bat, as opposed to Kingdra, who needs to set up with DD (not saying that Kingdra is bad though, it's just that Azu's immediate power gives it the edge if needed). Azumarill can also utilize CB Aqua Jet to revenge some threats like Nidoking and Chandelure (and Darma, too!). Azumarill has an offensive niche as a core breaker, as previously stated. The nice bulk is also a neat asset.
Also, you peeps better consider this nomination
And to conclude this post, I'm gonna say that my Amoonguss nomination is also still standing.
Ambipom for E pls. It's terrible Pokemon who fails to do anything in battle.