Double jump...? thats in to many games. Ever tried double jumping in real life? 2nd time you jump (in mid air) it seems you dont get anywhere.
Id say a good ability would to be able to charge someone very quickly and slam it into a wall or use it as a shield as it rushes at the humans. but the defective to the ability is once it starts charginging it can only slightly turn and doesnt stop untill it hits a wall (which would stun it), or until it is killed.
Health : 250 (Roar Extra +120)
Looks like this maybe :