The best i´ve found yet is 3xSlimes. I still havent maneged to beat round 3 in rank S.
But it´s not far away... The 3 slimes can be found: #1 On the hill opposite of the autumn
church (On the way to Rydon´s tower) #2 on the backside just around Empycchu. #3 Just
outside Trodain castle... I dont know if night or day matters when you look for them... I
also heard that 3 robots are good. But i have only found one myself. Let me know if you
find 3 of them, or if you found another combo that can beat rank S

Three cyclops is another good combo especially their deathmove.

i think that the archfiend near tyran gully and the crazed collosus near neos are the two
best so far