Unkillable Driller

The idea here is simple: Use a combination if ice and melee damage to trigger vamp a billion times and stay healthy.
Crystal Nucleation feels fantastic to use if you know how to build it, which is much harder than it sounds. The ice trails it leaves behind benefit a ton from the damage and cold mods, to the point where not running at least one cold mod is massively gimping your freezing power. That makes T1-C pretty much required, since you want to be able to pick either cold or damage T4 (spoilers). T2 could be either range or ammo, but I find that the range feels better to use, especially since you'll be wanting to make sure you reach the ground. T3-A is our choice simply because flow rate doesn't help at all, and can actually be a bad thing for the weapon. T4 is where you have a choice to make; either you pick cold for even stronger and more consistent freezing power or you take damage so that your trail can more consistently kill smaller enemies by itself. Both choices make sense, I just like the increased freezing power personally. T5-B is just a really good option for both self defense and being able to run up and freeze mactera quicly for the kill, and synergises better with what we want to do than T5-A.
Secondary is a more take your pick option, since none of driller's choices here synergise super well with Cryo. I chose Microwave because it helps with swarmers and nadocytes, both of which would be annoying and chew through ammo otherwise. Plus, it can take out spitters at long range and even do some decent mactera damage in a pinch. Mega Power Supply simply makes the gun better, with more ammo and a higher dps. T1-A means you are better against those nadocytes and shredders, plus you can hit more frozen enemies at once for better cold radience value and overall damage. T2-B works best with our kit since we only intend to fire our wave cooker in short bursts, so cooling based mods don't do a whole lot. T3-B is the star of the show, giving us even more Cryo ammo efficiency by letting us fire into frozen enemies for both damage and cold on other enemies, spreading the effect. T4 is just a choice between two very niche options; I use the hidden 3rd option of picking neither and getting to have a funny looking tinker animation when I press reload. Objectively you should probably be running T4-A because it makes your nadocyte and shredder clear even better, but I find that the difference isn't that large in practice. T5-B turns the weapon from a decent crowd damage option to insane clear, because on stop of spreading freeze you're also causing explosions that chain between enemies and get the bonus damage against freezing enemies. A little bit of Cryo into a wave and turn on popcorn mode and everything dies; it's magical.
Other choices aren't as interesting, so I'll just list them all here: