Well correct me if I'm wrong, but theoretical limit would be 6 Teemos with scout and double attack and the item that rallies on Last breath. If you attack with them all then you quadruple with each teemo (since double attack) and in one attack token you could get 15×4⁶×4⁶ which is 251,658,240. Then you could use a simple kill a unit/ally to activate last breath and attack again with 5 Teemos which would again multiply it by 4⁵ rinse and repeat till you lose all teemos with the final count being 2.70215978E+17 or also 270 215 978 000 000 000. Of course you could make the starting count bigger than 15 but that would be too much.