Which kits are the strongest in the game at the moment?

Which kits have you folks found the most powerful / reliable / capable of carrying? I'd love to hear your thoughts and to learn playing different characters the right way.
Please share your approach as well the character itself. Like, is there a signature power combo that makes this character great? Or specific weapons / equipment?

My favorite so far is, to my own surprise, the Human Sentinel. 1 point in Throw for detonating; priming Shield Drain; 6 points in Barricade with shield restoration lvl 6 evolution; maximum weapon stability and weapon damage. Charger X for main weapon - it works surprisingly well on gold, and this is by far the best weapon class I have yet (tried Revenant, it's OK but worse). Much better than even Turian soldier with turbocharged Soned. But there are many weapons that I don't have yet, so that may change.
The gameplay is straightforward, yet powerful: put a barricade down, kill stuff with accuracy-enhanced Charger, SD -> Throw for tech combo as soon as it's off cooldown. Repeat until everything is thoroughly dead, and revive fallen teammates in time (Barricade helps with that, too).

Another solid choice is Krogan Mercenary (the flamer Krogan). Max Flamer damage, max power damage, strong melee damage with compromise in melee towards DR. Flamer damage output is OK and survivability is good, but its damage output is not awesome. Let's just say Vorchas in ME3 MP were much easier to dominate the scoreboard with.