The last phase of lindamea is just survival. Neither of you can die for 20 (really 10) turns so you just need to wait it out until you see the buff on him disappears. If you really want to cheese it, make sure he changes phases because of dot damage. This forces him to go first after the phase change making his buff last 1 turn less than yours.
For prince of hell, equip a weapon with a high stun rate and gear with counterattack. This way, you stun him before he can do much. Then just keep stunning him until he dies. Alternatively, use fear resistance and 100% evasion gear (soul from the wind boss works well here) to survive his initial attack, then stun him to death.