What heroes are most powerful?

The orange heroes are the best ones to get, most of the general orange heroes have good overall strengths, although a few are specialised. There are then season orange heroes designated as S1, S2, S3 and S4 (so far). These are generally specialised heroes in that the have skills that activate when they are leading a particular type of troops. If they are put in the right set up these S heroes are the strongest.

However the strongest orange heroes are the ones that you have the most skills unlocked and upgraded for. The S heroes are hard to unlock all the skills, so depending on your level it could be very hard to make full use of an S hero.