Killing Cronos in God of War 3 will unlock the silver trophy "Titan Slayer".
Cronos is a special kind of boss... he's more of a moving level. You fight against enemies which are spawned by Cronos. Cronos' Attacks are slow but very powerful if he hits you.
Just use your favorite tactics to kill the enemies and the rest is easy.
All God of War III Trophies:
Releasing the Floodgates
Burnt to a Crisp
Acquire the Bow of Apollo
Discover the secret 'Hades Arm' room
Kill Hermes and acquire his Boots
I didn’t do it... But I wish I did!
Kill the Poseidon Princess
Successfully entertain Aphrodite
Sever Gaia’s hand
Open the Gates of Tisiphone
Three Wise Men
Solve the Three Judges
Perform a 1000-hit combo
Rip apart 1 Olympus Sentry
Blind 100 enemies with the Head of Helios
Deliver 50 kicks to Hounds
It’s getting hot in here...
Burn 100 enemies with the Bow of Apollo
Summon every Soul with the Claws of Hades
Cover Kratos in 500 buckets of blood by killing the enemies
No Guts, No Glory
Gut 3 Centaur Generals
Hitting Your Stride
Upgrade any weapon to the next level
Acquire the Boreas Icestorm
Seeing things from a different perspective
Solve Hera's Gardens
Collect all of the Gorgon Eyes
Collect all of the Phoenix Feathers
Are You Horny to Win?
Collect all of the Minotaur Horns
Completely upgrade all weapons
Beat the game
Up to the Challenge
Beat the Challenge of Olympus
Beat Titan Mode
Collect all of the ‘Godly Possessions’
Beat the Labyrinth without dying or failing