I discovered every tank and enemy in a few hours,and killed the boss first time I fought him,I don't see how people could have problems unlocking or killing.
Bubble Tanks has a certain sense of control that not everyone can grasp right away. Especailly when they choose a tank that they find they do not like and don't know what they should pic next.
The main reason I made this guide was to help compare all the tanks with each other not only by what they can do but with looks too. Now you have to admit, it is pretty cool to see all the final forms of the tanks right next to each other so you can compare how huge they can get. = )