The semi final boss was tough until I realised what to do. There is ALOT of slowdown, disappearing bullets and its not clear when your doing damage to alot of enemies and bosses always. When the screen flashes it means your damaging one of the 3 cores. Though this may have not been accurate when I was using charge shots, since the cores never died and the screen flashed. Line yourself up with one of the three collumns, wait for a rotation of one of the barriers in front of you, then pass through immediately. Keep firing on the core you are facing, then repeat this for the other two. Use the front attachment to sheild yourself from the bullets.
1