The following section of our Devil May Cry 5 Guide describes the first fully-fledged boss fight in the game - with Qliphoth Root.
Qliphoth Root in Devil May Cry 5
Where to find it: Mission 01 - Nero
This boss is very easy to kill, the only obstacle can be a relatively low skill if you're not fluent with the game's mechanics yet. Attack the main body of the boss using combos and the metal prosthesis.
In the background, the enemy will attack you with powerful tentacles, but they are very slow and you can easily avoid an attack. The roots are actually an introduction to proper gameplay and boss fighting - treat them as a foretaste of upcoming confrontations.