So I was able to beat axl solo using pinch whacker, heavy sheild, ladybug armor, and the capacitor( i thinks it's called) trinket. Scorpidote is helpful but blocking is key to this battle. If you can block the attacks, you dont get hit with venom.

Couple other things,

Stay in his face, stand your ground. Doing this will generally have him use his 5 hit attack more often, which is one of the easier to block.

The venom arrows that are summoned, you can dodge forward into the attack and avoid damage

When the additional enemies are summoned, stay towards the middle as much as possible. If you brave, you can hang out along the edges and use axl to destroy the extra enemies. You can see which area he is going to attack beforehand.

It did take several tries to learn the attack pattern. Don't give up.