Energy blast 1- D,F, punch button
fury kicks- D,B, kick button
fake roll- D,B, Punch button
koryuken - D,F,D,F Punch button
Something to fierce dp.The most powerful regular combo in the game. Kens dp also has a HUGE random factor to. Many combos can very quite drastically. A combo might do50%one time, then the next 65%. In general aim for something,(after a jump in/cross up)duck kX2, stand mk/duck k, stand mp/ or duck k, duck hp/to fierce dp. The latter can literally do about 80% on akuma depending on the random factor of the game. And in general combo to fierce dp is a safe bet to always at least do 50% on everyone in the cast. Remember that stand mk moves you foward, making combos much more lax. This combo also does good dizzy, however ken is not in a great position to punish if the opponent rolls so be on your toes.
Combo to fierce dp. Its the most powerful combo in the game.
Duck fierce, jab roll repeat. Duck fierce has tremendous priority and although not a true combo most characters do not have a attack that is fast enough to beat it. And if they do, the priority is not good enough to beat the duck fierce. Duck fierce will actually even out right beat "weaker" reversal moves(like guys hurricane kick)so your opponent is forced to throw to beat the trap, AC, or reversal(again assuming there reversal has enough priority to beat kens duck fierce in the first place). Note of course the problems with this being in the corner ken can roll through certain ACs etc. And for throwing, well roll is invulnerable to throws and if you are doing d/b fierce you will automatically tech throws. You get the idea. Very effective for what it is. Obviously there are other variations but this is a basic idea.