Azumarill just hits like a truck, and it has plenty of resistances to boast too in Water, Fighting, Dark, Bug, Dragon, Ice, Fire. Jesus, that's 6 popular attack types that give Azu a chance to wreck you shit. BellyAzu may be overrated but it's still a threat due to its ability to switch moves (Waterfall / Play Rough + Aqua Jet can KO a good amount of things) and the everlooming threat of a Belly Drum on the switch blowing the shit out of your Skarmory / Gourgeist / whatever physical wall you have that doesn't resist one of its STAB and is unfortunate enough to be unable to KO / outspeed. And of course CB Azumarill still hits like a bitch and has an STAB stronger than Waterfall and can use Superpower too, meaning non-physically defensive Ferrothorn kinda just dies on a wrong switch. Fortunately, checks like Sludge Bomb Tentacruel and Mega-Venusaur exist, and Azu is much easier to check than outright counter.
Klefki is an awesome supporter, it can do whatever your team sees fit. It can use Spikes, which it can spam against things that cannot KO it quickly, and it has both Prankster Thunder Wave & Dual Screens, both of which can not only halt the opponent's sweepers but also set up your own sweepers to roll right through them, especially with the help of Spikes by yours truly. Foul Play even comes as a nice tool for stuff that think they can setup on Klefki, like Aegislash and Garchomp.
They're the only Fairies I've tested so far, but I'm really liking them. Psyched to know what the other esteemed Fairies like Togekiss and Mega-Mawile can do.