Hawke is a Black Hole CO with slightly stronger than average units and strong, but relatively expensive CO Powers.
Playing as Hawke
Generally, Hawke is a straightforward CO to play, playing similar to COs such as Andy or Olaf, with a slight offensive boost. In maps without Comm. Towers, Hawke's increased attack will allow him a slight edge over more specialized COs, while also allowing him to keep up with Von Bolt's increased defense, a trait that gives a lot of other COs trouble in maps with no Towers. Conversely, Hawke is also strong on maps that do have towers, as the Tower boost combined with his own boost allows him very reliable 2 Hit KOs against units on cities, notably Tanks versus other Tanks. Given his abnormally long CO power bar, Hawke will largely have to rely on this Day-to-Day power to keep from falling behind.
Despite their expensive costs, Black Wave and Black Storm are both strong and versatile powers. Given the length of the bar, a higher quantity of units, and likely some higher tier units such as Md. Tanks and Rockets will have been deployed from either side by the time Hawke's power is ready. This will maximize the value of Hawke's powers, as the damage dealt and healed by his powers is the same to all units, regardless of type. The other strong point of the power is that it can be effectively used at almost any point of Hawke's turn, such as after attacking with full-HP units, healing them right afterwards. The main shortcoming of this power is that due to its cost, Hawke will have to sustain a few CO Powers from his opponent before he can use his own. If Hawke can survive until that point, however, a well-timed Black Storm can be a game-ending power.
Playing Against Hawke
Being an All-Around CO, Hawke has no particular weaknesses to play around. His Day-to-Day, while strong, pales in comparison to those of some more Specialized COs, however. Hawke will still have a bit of trouble competing with Max in Direct Combat, for example. Use this to your advantage and establish a lead over Hawke before he can use his CO Powers, preparing to minimize losses whenever he nears a full CO Power Bar. No unit is safe from Black Wave/Storm, but if Hawke cannot capitalize immediately on the damage dealt, it is a rather underwhelming power. It is best to assume that an opponent playing Hawke could fire off a Super/CO power at any given point, so care must be taken when planning, even if his CO Power bar is not 100% full yet.
Sasha in particular is a good CO for combating Hawke, as her CO Power is very effective at denying Hawke the ability to use his powers for a very long time. Without his powers, Sasha can establish a unit advantage through her own Day-To-Day, giving Hawke trouble through a higher quantity of higher-tier units. She will not be able to delay Hawke's powers forever, but can delay it long enough to establish an advantage that would be hard to surpass, even with Black Wave/Storm. Andy's CO Powers can also help alleviate the pain of Hawke's powers, but this may not be ideal as Andy's lack of any offensive boosts will give him trouble before CO powers are even factored in.