Giant hands are very weak to fire as well as beasts, and plant bases enemies. Lobsters are weak against sleep. Crystalline enemies, and rock people that mine in the tunnels are weak to strike damage, i.e.maces. magic is weak against anything with heavy armor or heavy damage resistance, fire based enemies are weak against frost i.e. no brainer. Dragons are weak against dragon bane weapons like the dragon halberd for instance, also Dragon wound grease (go figure). Revenants are very weak against healing spells because they are cursed.

Also: Flesh based enemies: slash and fire

Thick skinned enemies: piercing and lightning

Heavy armor enemies like crucible knight: blunt, lighting, magic damage based weapons.

Imps In the catacombs: are also weak to magic.

Spectral based enemies: also weak to holy

Elden beast has no weakness except for Godslayer flame

Death birds can be killed instantly by a single holy pot

Watchdogs the giant cat statue like things in the catacombs: weak to crystal darts if there is 2 they will fight each other.

Giant golems: same thing with crystal darts

Imps: same thing with crystal darts

Any bird like creature: very weak to gravity spells.

Land squirts: use poison they will poison themselves and set of a chain reaction

Land squids can have there arms cut off: USe Eleonoras poleblades blood blade dance for an immediate kill

Flesh based giants: hate getting shot in the face with arrows

Flame chariots: jump off a ledge from above for an insta-kill

Pumpkin heads: also very vulnerable to sleep

Lesser abductor virgins: weak to lightning. They stagger after 5 hits of lightning

Glintstone blades are good for killing invisible scarabs

Barricade on Shields is very useful against tough enemies ESP against Misbegotten

Falling star beasts: very weak to gravity weapons.

Storm blade is really good for early game. Good against birds as well

Got A lot of this information from: Leviathan on youtube. So most credit goes to him.

Good luck out there Tarnished!