IndigoGollum
The Destroyer
When an enemy in Terraria takes damage but is not killed, that enemy becomes invincible for a short period of time. This can be frustrating while the player is using minions, as the minion may hit the enemy, dealing weak damage and preventing the enemy from being hurt or killed by the player's other stronger attacks. This could be fixed by shortening the amount of time the enemy is invincible when hurt by minions(or sentries because they also deal summon damage).