Apsalus.

[Anzac-A1]

Gonna say it. Apsalus is literally the worst boss so far. I still can't beat the first Quest one, even on the lowest difficulty. So many of its attacks can't be avoided, since there's no room.

[Eruend]

It's not that bad. Just don't melee it unless it's knocked down.
Maybe upgrade your part's levels too.

[TheDpepol]

and even worse when you managed to damage it well the large portion of its body got very huge damage reduction. but yea if you are in early level and cannot level up parts they are basically forcing you to change parts and test other part abilities

[Vivianite]

go for it's head + body + floater (the piece directly under the body) then knick at one of the sides, it'll go down ezpz

[Anzac-A1]

Managed to do it. I used an overall Exia build, with dual GN Sword IIIs (ranged and melee). If you use Trans-Am, you can annihilate each health bar.