Sash Lilac being Stunlocked by a DNA Cannon in Sky Battalion.
Stunlocking is the process by which enemies and bosses repeatedly attack the player before they have a chance to regain control. Under normal circumstances, the player is invulnerable for a brief moment after being hurt by an attack, but certain enemies and bosses can override this rule with their special attacks. Milla is the most vulnerable to stunlocking, since she has the least Health Petals (which is 4).
In Freedom Planet, some of the attacks that can Stunlock include Serpentine's Bullet Rain, the energy waves from DNA Cannons (pictured), lava in Thermal Base, and the energy bolts from Sparky in Battle Glacier. (Maybe you can also count the giant laser in Final Dreadnought 4)