I think an audience would assume “superlaser” refers to Death Star-level firepower.

I honestly kind of liked the idea of connecting the laser cannons to the dreadnought we saw in TLJ, but I did feel like “dreadnought-tier” was a bit of a mouthful. You could just call them “dreadnought cannons”. It separates it from Death Star levels of destruction, but keeps the description simple while still connecting it with pre-established technology.

So, you could do something like DZ’s suggestion, but like this:

”Their fleet’s dreadnought cannons leave us massively outgunned”