...the difference between electromagnetic radiation (light,
radio waves, etc.) and ionizing radiation (alpha, beta, gamma, etc.).

that's why I said radioactive (i.e. ionizing) =^^=

       Is the big gnarly thing Zed blows up the mountain with supposed to
be an x-laser?  (Kewel 'splosion wasn't it?)  I think animators just throw
in lasers most of the time 'cause they look better than ordinary ordnance.

I would guess x-ray or particle beam of some kind. The other reason for
putting lasers on spaceships and mecha (besides them looking hi-tek) is
mass. Assuming that you have a way to generate almost infinite power with
very little mass (oops! that may be a hole right there!) you can blast away
and make big kabooms without having your mecha sink into the dirt. You don't
have to dedicate so much interior room to ammo storage.

On a somewhat related topic, weren't the kats lucky that Mutilor wasn't very
clever? If I wanted to steal water from kat planet, and had a kickin
spacecraft, I'd get some rocks headed for the planet at a high fraction of
c, sit back,  and let them do their work. Oh, it might boil off the top few
meters of ocean, but you don't have to deal with any objections from the indigs!
=^^=