Actually, honestly, I feel that Feraligatr should be knocked down to A rank or A- rank.
Did I mention that it gets hard blocked by very common stuff like Seismitoad, Vileplume(with speed), Poliwrath, Cacturne?!, Ludicolo, Ferroseed, I can go on...
+2 252+ Atk Life Orb Feraligatr Ice Punch vs. 252 HP / 252+ Def Vileplume: 322-380 (90.9 - 107.3%) -- guaranteed OHKO after Stealth Rock
252+ Atk Life Orb Feraligatr Ice Punch vs. 252 HP / 252+ Def Vileplume: 161-192 (45.4 - 54.2%) -- 95.3% chance to 2HKO after Stealth Rock and Black Sludge recovery
+2 252+ Atk Life Orb Feraligatr Return vs. 252 HP / 252+ Def Seismitoad: 235-278 (56.7 - 67.1%) -- guaranteed 2HKO after Stealth Rock and Leftovers recovery
+2 252+ Atk Life Orb Feraligatr Return vs. 252 HP / 252+ Def Poliwrath: 204-240 (53.1 - 62.5%) -- guaranteed 2HKO after Stealth Rock and Leftovers recovery
Not going to bother with Cacturne and Ludicolo because they are definitely not counters. Cacturne is pretty decent check as it can't be hit with Aqua Jet and Sucker Punch does around half. Ludicolo isn't even really a check, it's 2HKO by 252+ LO return even with 252 hp. Ferroseed is very solid counter.
Basically, you can't reliable counter Feraligatr without knowing whether it's SD or DD and without what 2 moves it has out of Aqua Jet, Ice Punch and Return. Not only that, pokes that can check it like Seismatoad and Poliwrath don't have reliable recovery and can't do much back to Feraligatr besides statusing it with Toxic or a lucky Scald or phazing it out (Poliwrath). While these two can break down Feraligatr to the point where he can be revenged or that he'll die from status or LO, they certainly don't beat it one on one. Vileplume can check it but to do that reliably you have to sacrifice a poke to get Vileplume a free switch.
You also that Feraligatr is set up bait for Omastar
252+ Atk Life Orb Feraligatr Waterfall vs. 4 HP / 0 Def Omastar: 133-157 (47.1 - 55.6%) -- guaranteed 2HKO after Stealth Rock
and Gorebyss
252+ Atk Life Orb Feraligatr Return vs. 252 HP / 0 Def Gorebyss: 133-156 (42.3 - 49.6%) -- 89.1% chance to 2HKO after Stealth Rock
and Shiftry (It could stay in and OHKO Shiftry if it decides to set up so certainly not. You must by very confused by the term set up bait.)
Barbaracle (you say it "eats +2 Waterfalls like a man") (no hp or def on calcs cause it's supposedly set up fodder and you don't run those evs with shell smash)
252+ Atk Life Orb Feraligatr Waterfall vs. 4 HP / 0 Def Barbaracle: 142-169 (49.6 - 59%) -- guaranteed 2HKO after Stealth Rock
+2 252+ Atk Life Orb Feraligatr Waterfall vs. 4 HP / 0 Def Barbaracle: 286-337 (100 - 117.8%) -- guaranteed OHKO
I wouldn't be completely opposed to Feraligatr being A rank because it's fairly easy to revenge or wear down, and arguably best thing to revenge it with is arguably the other most dominate poke in the tier (Shiftry). But to say it's set up bait or easily countered is completely false. Feraligatr is similar to Sigilyph in that you cannot effectively play around it until you know it's moves, items, and what speed it's running (not saying that it's common or advisable but Jolly Feraligatr beats Adamant Shiftry).