Well, In my Opinion only 2 fighting types from B/W are stronger than the other fighting types.
1st Option:
Conkeldurr @ Flame Orb
Trait: Guts
EV's: 224 HP / 252 Atk / 32 SpD
Nature: Adamant
-Drain Punch
-Mach Punch
-Payback
-Facade/Stone Edge
Okay, Conkeldurr is one of the Stronger Fighting type Pokemon is B/W. Conkeldurr is just a great Physical Attacker. When Flame Orb activates it's attack is off the roof. Drain Punch is STAB and heals Conkeldurr from burn damage, Mach Punch is Priority to revenge-kill faster Pokemon, Payback is good when teamed up with Conkeldurr's horrible Speed stat, you can either use Facade/Stone Edge. Facade is good with Conkeldurr's burn and Attack stat, but if you use Stone Edge you can hit Flying Type Pokemon.
2nd Option:
Mienshao @ Life Orb/Normal Gem
Trait: Regenerator
EV's: 252 Atk / 4 HP / 252 Spe
Nature: Jolly
-Fake Out
-Hi Jump Kick
-Stone Edge/Acrobatics
-U- Turn
Okay, You can either use Life Orb or Normal Gem. Normal Gem is good with Fake Out which increases Fake Out's power and then you can use Acrobatics which doubles when the user has no item. Fake Out, is for free damage and it flinches your Opponent, Hi Jump Kick is for STAB, Stone Edge is for the Flying Types Or if you use Normal Gem as your item use Acrobatics, U-Turn is to get out of Situations and getting your health back (this move is good with Life-Orb)
So these are the Strongest of Fighting Type in B/W, Hope this helps :D