Get cloaking tech and stellar manipulation ASAP. Also, use Intel to make sure he can't detect your ships. Then, simply park a cloaked starkiller over his homeworld star and watch the fireworks over your victory celebration.....
no, but really, this is almost ALWAYS a good idea. If you've got at least one - several is better - starkiller(s) parked over his homeworld star, preferably accompanied by a cave troll of a defensive fleet, you've got something to bargain with -
his life.
Also, use Fighters. Lots and
lots of fighters. Use their to-hit bonuses and your race's ability to outproduce him to face him with swarms of nasty little buggers which have a fairly good chance of hitting his ships and a reasonably good chance of evading his shots.
Note: I myself have no experience with Devnull, so my advice could very well be an empty piece of text.