Plasma Destroyer is a plasma cannon with a 72" range. Also, Wolf, it's not necessarily a variant just because it uses the Leman Russ chassis. The Basilisk uses the Chimera chassis, but it is not considered a variant of the Chimera. The chassis has been heavily modified to the point that the Basilisk is its own chassis with its own variants.
*sigh* I have to point out that despite what you see in games, lasrifles win wars. Just because lasrifles suck at killing superhuman killing machines in power armor does not mean that they are bad weapons. You are shooting them at the wrong targets. The most common enemy the Imperium faces is lightly armored humans armed with lasguns or autoguns, NOT SPACE MARINES.