Dead Cells

If you want to make this as easy as possible on yourself, you can do this with zero cells active (0BSC) , and you can enable any options in Assist Mode that you want. Specifically, you can lower enemy health to 20% to make the Giant a quicker kill, and turn on infinite deaths so you can simply try over and over without replaying a run to this point.

The build I used was the repeater crossbow/quiver of bolts combo, upgraded to VI-S, along with Wings of the Crow (XI-S). As soon as the battle started, I triggered Wings of the Crow and hovered above his right fist, firing across at the other fist with the repeater crossbow. Once he takes enough damage, the eyeball appears right in your line of fire - you don't even have to move. The eyeball goes away, the fist is back taking damage, then the eyeball appears again... I barely moved for the duration of the battle. On zero cells with the enemy health reduction from Assist Mode, the entire fight takes less than ten seconds, and the Giant never really had a chance to attack.

The path to the Giant requires going through Caverns on 0BSC, as the Forgotten Sepulcher route is only available at 2BSC or higher. With no paid DLC, your best route is probably PQ -> Toxic Sewers -> Ancient Sewers -> Insufferable Crypt -> Graveyard -> Cavern -> Guardian's Haven. With the Bad Seed DLC, you could skip the first boss battle by going PQ -> Dilapidated Arboretum -> Morass of the Banished and then sacrificing a Mushroom Boi at the altar there before proceeding on (assuming you are lucky enough to obtain that skill before getting there). You'd then skip the Boss at Nest and proceed on through Graveyard and Cavern as usual.