In a Tower Defense game like ASTD X, the best way to make any underperforming or less powerful units more potent than before is to add a trait to the Unit. While a few traits may look good initially, they won't be that viable as you progress and take on more formidable enemies. To clear all your doubts, here is the ASTD X Trait Tier, which helps you understand the difference between the best and the worst.
