Buy black spirits, max out "Far East Weapons" and equip enchanted weapons that give a lot of additional damage. With that, I conquered the world without using any other soldiers easily.
It is quite like epic war 3, but there are several great improvements. Firstly, the upgrade page looks a lot better and is more convenient than the cards. Secondly, hard and epic mode is a good idea. If you don't want the game to be too difficult, you could only play easy mode, i.e. you could choose the difficulty of the game. But there could be some improvements. It should really have a speed up button and a pause button. It would be nice if you could give orders when the game is paused. Secondly, you need a button to the menu. Once I realised that I forgot to arrange the units I recently bought, and I couldn't get back to the menu. Finally, it really needs autosave. I appreciate your good work, and I'm sure those requests wouldn't be difficult with your expertise in flash games. If you could spent a little time and add those improvements, I'm sure people would like your game a lot more. As you could see, many are complaining about those.
Big problem! Invincibility ( the bonus ) doesn't last forever after buying infinite bonus! Well, you don't expect the "invincible" to last forever, do you?