The only really really hard fight is the one involving the minotaurs. Some spoilers - after that go to the plant people camp and recruit the fat plant guy that can resurrect dead things and use him to resurrect the minotaurs. Instant win in everything.

Larian's Biggest Oversight, what to do about it, and My personal review of BG3 EA
"74.85% of you stood with the Tieflings, and 25.15% of you sided with Minthara. Good outweighs evil, it seems."