I'll stick to just FFV

Archeoaevis - Death Claw works on it's first stage Level 5 Death during it's revived stage

Purobolos - Use a party of Beastmaster's with Control and make them all use Self Destruct.

Ramuh - Either use Silence to cripple him or just outright cripple him with Blue Spell Death Claw which will allow you to kill him in two moves.

Sandworm - Kill him with one cast of Blue Spell Aqua Rake

Adamantoise - Level 5 Death

Soul Gun Launcher and his Gunners - Level 5 Death and then just pistol whip the Soul GunLauncher with Bolt magic

Chimera Brain/Manticore - Death Claw screws him over... Stop as well

Tyranasaur - Phoenix Down

Carbuncle - Summon Catablepas

Ex-Death - Use Staves of Light to cast Holy on him, doesn't outright kill him but makes this a really easy fight...

Shield Dragon - Control and let it kill itself.

Omniscient - Berserk him to cripple him.

Phobos , Nerid, and Triton - A party of Bard's with Requiem will destroy them, or you can use Odin...

Bahamut - Stop will sometimes work

Leviathan - Coral Rings will make this boss a push over

Azulmagia - Ether punish him with Bio, or use Self-Destruct on him so he can learn it and use it on you...

Alte Roite/Jura Aevis - Use Berserk on Alte Roite and it cannot transform into Jura Aevis.

Twin Tania - Summon Odin when it starts charging up Giga Flare.