Ash is a flying, mobile unit with high siege bonus. Dealing low damage, Ash is not suited for regular combat. Instead, she excels at sieging while your other units pressure another objective. Escorting Ash to the enemy SENSO-Gate as you would a Siege Tank is a handy strategy to deal direct damage.
Ash's achievement is:
Destroy troops with ASH.
Ash has a very low damage output, though her high mobility can help you swoop in for the kill. Often times your enemies will have to be weakened beforehand.
At tournament standard
Ash has 315 health and 79 damage at level 3, destroying these units in one hit, ignoring armor or evasion: