Have you tried a mech with an anihilator cannon?

Make sure you have the mission to kill this active before trying again. These are actually super rare finds and you got lucky here. Fortunately, if an area can spawn the Megarachnid, it will keep spawning in that area, so I'd make a point of bookmarking this location.

The spider swarm is definitely the real problem here. You need some kind of group piercing attack to take care of the mob which will continuously regenerate, and you will find yourself spamming nanowraps to keep yourself afloat, too. Flamethrower-style weapons should work (and if you're short on those there's a vanilla quest reward weapon you can go for) or anything with the Screw Attack secondary will make short work of the swarms and also the Megarachnid themselves, although if you for a melee strike against this thing you will be spamming nanowraps even more.

It works, though. I got the quest completed and then didn't bother trying to farm these things. They're nasty even if you're well prepared.

I looked at the frackin universe wiki and the megarachnid has 90 health and -50% fire resistance.

Fair enough. I'll admit that I haven't actually attempted to kill the Mega with a flame weapon so that's egg on my face there.

Mind you I said *Flamethrower-style* weapons - the key point is the weapon shoots a cloud of damaging stuff *through* enemies. Attacks that hit groups are essential to winning this fight.

There's a "plasmathrower" broadsword in the Armory that deals electric damage. If fire damage is out, try that.

I did manage to eventually kill the megarachnid but advancing slowly towards it and using the matter manipulator to set up walls in front of myself, which I would then take down and rebuild farther out. I eventually managed to get right above the beast, and used the matter manipulator to trap it into an area it couldn't get out of. Then I used a secondary firing mode on one of the heavy weapons (don't remember which one) that fired through walls. It took me almost five minutes of shooting (wearing tier 6 armor) to kill the megarachnid, so it definitely had a LOT more than 90 health.

Later, I encountered more megarachnids on a radioactive planet, but these were much weaker and I was able to kill them in a few shots. The one on the shadow planet was far more powerful.

Piercing shots, maybe bring a fully-upgraded Grinder.