As suggested by the description, the player can use Kai to complete this achievement. Kai has stats comparable to QP and is thus similarly versatile, the only difference being a buff to attack which makes his combat capacity slightly better. His Protagonist's Privilege is also battle-oriented, and if used correctly, can make him nigh invulnerable for short periods of time, and is especially effective against high-attack opponents with traditionally weaker defenses.
The player can use any unlocked characters to complete the campaign, as the character can be switched before the match starts. This enables the player to switch to a sturdier character or one they are more comfortable with.