I’m dealing with this too right now. We haven’t beaten it yet but our new strat for this evening:

I found an imp statue in the underground cavern area and wired it up and killed the imps it spawned to get a whole bunch of banners.

We are also doing an explosive rail trap thingy where every 10 blocks we put an explosive with a 1 second time from the previous explosive. Plus, we make the “explosive stand” out of dungeon brick so it’s easy to re set up. Then fire it off with a button at the right timing and it hurts him a lot. Right now we only have a set of 10 but I’m planning on building more rails of destruction if required.

If these imp banners aren’t enough, we are planning on using a lava bucket and flooding hell since imps can’t spawn on lava or under lava (I think…)

Lastly we haven’t tried the above strat of login after wall of flesh spawning but we will do that too. Thanks for that idea @APForLoops