I feel like there's a certain amount of, well, dramatic tension that's missed here. How much fire and light - and since these creatures hate light, where do they live?
With modern LEDs, and maybe future ones flashlights are very efficient. We used to go from 'we need to top off the battery every 2-3 days' to weekly or even monthly top offs.
Lets assume small amounts of light drive them off, sensitive eyes and all that, but you need something truely powerful to hurt them. I do like the idea of 'cutting' grade lasers and bright lights as 'weapons' and smaller lights for normal use, with batteries running out for dramatic tension.
Apparently google used to give these out as swag in the good old days - Adam Savage has a review of it. Basically its a baton that happens to hold batteries and lots of bright LEDs. It lasts a total of NINE minutes on its full batteries. If you're hunting down creatures that hate the light, you'd probably want 'seeing' lights, and something like this.
As for fire, if I was fighting an elephant sized one or a small plague of them, something like a TOS-1 or 2, and more importantly thermobaric ammunition would be nice - . I believe there's smaller RPG sized versions as well. Its more for open spaces or when you can launch something across a large open space. However inside a confined space something that causes lots of heat, fire and sucks out all the oxygen would be a bad idea. Likewise white phosphorous burns and keeps burning but causes oxygen deprivation -it would be perfect other than the smoke (which IIRC also does a number on thermal/night vision gear) and potentially killing your own troops
Flamethrowers are messy - they're large, need tanks and impede mobility but I'd certainly want incendiaries. If low tech, molotov cocktails might work. There's little balls used for fire suppression burns and having something with its own oxidiser is a good idea. Thermite mines might be an idea, or similar incendiary devices