First, I would like to tell you, Rock Slide and Aerial Ace are awfully weak, even with STAB. They needn't to be included on a such Pokémon as Greninja. However, I counted them while searching, and found out that the combination Grass/Rock has the most Supereffective hits, scoring 327 Pokémon hardly hit. However, you will hardly see Rock Slide and Grass Knot on the frog, anyway, and a least abnormal set would involve Ice Beam, Surf, Dark Pulse and U-Turn together. but if you want to play the supereffective key, go for HP {FIRE}, Surf, Grass Knot and Ice Beam and you'll score 444 Super Effectives. Furthermore? There is Grass Knot, Ice Beam, Power-Up Punch and HP {GROUND} which is simply awful but scores 528 Supereffective, but I strongly not recommend it.
I hope this helps.
~ Sincerely yours, Blitz.
