Skeleton King because of tons of health broken abilities and lots of good combos to go with him
All supercell games are good but my fav is definitely this one and has some much potential
I recommend buying things like hero's, dart goblin due to its ability to increase its speed every attack, and witch because of the summoning is way to good(from shop btw).
Also when you unlock gizmo's try using mortar or hot pot because they will do insane damage.
I definitely recommend this game
I do wish there are easier ways to get money due to expensive characters in