Just dig out a giant circle underground with platforms and run around the edges shooting at it.

Most bosses can be easily defeated by building the proper "arena"

 

We used the 100 block teleporter area and dug 10 blocks up and @Bountyhunter3232 had a melee baghnakhs set up and went all in and just drained her from 10,000 to 1,000 then i finished her off it was crazy

This isn't the first time fighter her btw this is probably my 60th time counting respawning and many different playthroughs

 

Damn right I did!

 

We beat Moon lord last night...again and we started a new expert playthrough

 

Me and Bounty started a new playthrough for Journey's end...it was fantastic!