Bombard X: A cumulative, static ability that means, "This unit may attack a unit in the Ground arena instead of the Space arena, using X power plus any other effects." You choose whether to use Bombard to attack a unit in the Ground arena or to make a normal attack in the Space arena. You can't attack a unit in the Space arena using Bombard. Power changes affect Bombard.
Riposte
Riposte X: A cumulative ability triggered by the roll of a natural two during an attack that means, "If the attacking unit rolled at least one natural two against this unit, this unit does X damage to it when the attack ends." Only one natural "2" is counted from the attack roll after re-rolls. Negative Accuracy can't decrease the die roll to a natural "2". However, you or your opponent may use an effect to re-roll dice to affect the number of natural twos. (You only count the 2, if any, from the roll used for the attack.) Riposte applies only to dice rolled for an attack, not to dice rolls for abilities like Retaliate.