I honestly find myself completely forgetting that my polaris even has a charge attack. Currently the charge attack is just a pre-expanded bullet that does ~1.5x the expanded bullet damage, or ~2x the unexpanded. In the time it takes to charge and fire it, you could fire three regular shots.
Idea 1: Malfunction overload.
Charge attack would shoot out a regular expanded bullet, but the gun would also have a "overcharged/malfunctioning" explosion, roughly equivalent to a super blast bomb explosion centered on the player. (almost identical for the supernova, elemental/shock themed for the polaris)
Idea 2: Shotgun blast. (Stolen from another thread)
Shoots out a volley of 3 expanded bullets, fanned out similarly to either the DA charge (a wall of 3) or staggered to the left, right, then center.
First idea +1
Second idea -1