In Mortal Kombat 3 I typically used Sub-Zero. He was by far the strongest in my opinion in Mortal Kombat 3.

When Ultimate MK3 came out it was anyone with a pop-up ender that you could time and jump in for a jump-in auto combo and repeat for a near unlimited combo. Classic Sub-Zero and Human Smoke were my two mains here.

When Mortal Kombat Trilogy debuted I stuck with Rain.

His Mind Control Orb is op asf.

Ermac is my main as his tele-slam and teleport punch allow for some insane damage combos in UMK3.

'o' same

Sub Zero and Sektor...

Sub has always been my main and very strong in (U)MK(3)(T) i believe his best combo was: HP, HP, LP, LK, HK, Back+HK ending with that awesome roundhouse kick =)

Sektor was my 2nd main. I always found him a interesting character in MK3. But UMK3 came jump-in and pop-up combo's and Sekor was my absolute juggle-combo master. Making people crazy with the (Seeking) missile / teleport / jump-in / pop-up. And I loved his grab with that extra little robo-arm.

grts

Mortal Kombat 3 it would be Sub-Zero. He is by far one of the most powerful fighters in this version seeing as how his Ice Clone can be done virtually anywhere trapping people.

Ultimate MK3 I'd go with either Classic Smoke or Classic Sub-Zero. Their infinite combos are so easy to pull off on anyone in the game. Smoke is by far stronger than Sub-Zero but Sub-Zero's infinite is easier to pull off than Smoke's and has more hits than Smoke's.

Mortal Kombat Trilogy it is Rain by far hands down. Not due to his infinite combo it is more because of how secretive he really was in UMK3. His Roundhouse is my favorite move by far and his Lightning Fatality is sweet too.