This page in our guide to Devil May Cry 5 contains a walkthrough for the boss fight with King Cerberus. This fight is nostalgic for those who have played DMC 3 - Cerberus was the second boss in that game.
King Cerberus in Devil May Cry 5
Where to find the boss: Mission 17 - Diverging Points: Dante
The boss has three heads - each one of them creates a different aura and allows the boss to use specific attacks. The boss starts the fight by using the head controlling fire. King Cerberus will attack you with his paws. Avoid his attacks and watch out for the flames that will appear under Dante.
Put out the flames - when you do that, the enemy will start charging the next element. Run away from King Cerberus to avoid a powerful AoE attack. After that, you can go back to attacking the boss. The head that uses electricity shoots out beams that will damage you from a distance. King Cerberus will also attack you with his paws covered in thunders. Deal enough damage and the boss will fall down for a moment - this is your chance to deal a few free hits.
The enemy will start charging another element - ice. Move away from King Cerberus to avoid damage. Start attacking him when the head controlling ice is active. Here, the boss can, e.g. throw icicles at you and use frost breath.
Besides using different elements, the boss can also charge at you when Dante is standing away from him. He can also use his paws to damage you. The key to winning this fight is to run away from King Cerberus when he is switching to another element. Use Trickster to avoid his attacks.