Now that I've fully read OP, here are my picks:
Adept
Judgesticar. Can tank, excellent AoE damage, quick cooldown, and can deal with all things quite well due to Reave H4x. Tied with Drell adept. Drell switches tankiness for pure DPS. From an Avenger to a Predator, the DA build I've created can make ANY gun look good. Fury comes close but is more vulnerable with my in-your-face playstyle.
Soldier
Number 1, N7 Destroyer. With PPR/Typhoon/Piranha/Spitfire, everything goes down effortlessly. Quick shield recharge and Hawk Missiles keep enemies like Phantoms too busy to strip your health. Runners up are TSol (not Havoc) and Geoff Troopa. TSol can take damage and dish out twice as much. Only limitations is lack of great CC and dependance on weapon choice. GT weapons build with shield Flamer makes everything a joke. Just slap on the Prothean Party Rifle and he can melt all the things. Runner up, BatSol. Top tier CC, and the most OP DoT in the game. Fast and durable to boot.
Engineer
The aforementioned QME; however I don't have debuff things because they're already dead. Runner up would be GE. Only problem is a lack of power-based DPS. My turret is a medic.
Sentinel
Paladin for the aforementioned reason (walking tech WMD, bullies nearly all units). Don't even need strength enhancer for my Hybrid build. Valkyrie as my number 2. My playstyle involves sticking and moving so I'd warp~dogde, a tactic that doesn't get used by others. Asari dash can cancel out the animation for warp allowing you to dash in or around enemis immediately after the warp projectile is cast. Number 3 is TSent. The true Jack-of-All-Trades of the MP roster, whether it be my melee build or my weapons build, there's nothing he can't deal with quickly. I love the Evicserator on this guy and I can keep the Wraith under wraps for plat.
Infiltrator
Salarian, Shadow. SI is the OG of OP. His edge over GI is more survivability and being capable of tech explosions. I always feel like he's for an innate accuracy modifier with sniper rifles when I play him. Shadow is my favorite infiltrator and with my SS/VENOM build can deal with everything. SS can do ridiculous, nearly Javelin-like damage vs armor with an extremely strong heavy melee that nearly rivals the KroLord. ES is a fun detonator that can really suppress aggressive mooks.
Vanguard.
Novaguard and Cabal. Novaguard is the most survivable Vanguard in the game and with a biotic team full of casters even the geth get overwhellmed with ease. Great potential for a melee build as well. Cabal is able to synchronize any team type. With Turian passives and BF, she makes a perfect weapons build. With NB can shut down aggressive mooks and follow up with PS. She is perhaps the most maneuverable kit in the game as no other character can go from the middle of Ghost to the top right side instantly.