My players go for an (appropriately blessed) roll of Admech-issue duct tape. 

My players go for an (appropriately blessed) roll of Admech-issue duct tape. 

Your most powerful psykers can choke people with their minds and shoot lightning from their fingers?
 
Dawww. That's adorable.

Your most powerful psykers can choke people with their minds and shoot lightning from their fingers?
 
Dawww. That's adorable.

Your most powerful psykers can choke people with their minds and shoot lightning from their fingers?
 
Dawww. That's adorable.

Your most powerful psykers can choke people with their minds and shoot lightning from their fingers?
 
Dawww. That's adorable.

Your most powerful psykers can choke people with their minds and shoot lightning from their fingers?
 
Dawww. That's adorable.

I feel for you Tisis. 
 
But rather than fighting fire with fire (i.e. meeting his OP character with OP enemies), I'd suggest a different tack. Don't look for solutions in the rules - look for solutions in the story. 
 
Change the nature of play to make this nob's character useless. He might be a unstoppable min-maxed cheese tornado in combat; but I'll wager that's all he can do. Good. Spend a few sessions in roleplay-heavy non-combat. Engineer situations where your other players have a chance to shine. Engineer situations where the other players inadvertently screw with his powers/plans. 
 
All of these things are possible. He will eventually either decide that:
 
1. You suck as a GM. He's going to go join a game where he's allowed to indulge all of his powergaming, rules-lawyering dweebishness; or
2. Yeah. OK. That character's kinda stupid. Maybe he'll tone it down a bit. 
 
Both are wins. 

This is a very ambitious idea - one you'd really need the right group of players for. I reckon it could be absolutely amazing. 
 
One more clue/bits of flavour off the top of my head:
 
 - A warehouse, thought abandoned, burned down during the "missing" period. A number of bodies were found inside, but were quickly hustled off to the charnel houses. If the players are quick, they may be able to bribe/talk their way into one such house, finding that some of the bodies have obvious gunshot/melee weapon wounds.  

And if one of my players asked, I would consider slapping them. 

To my fellow GMs...I'd like your opinion.
 
I have a Dark Heresy campaign that is progressing well. It started with a couple of loosely connected adventures (mainly as my group had never played DH before and we weren't sure how it'd go); but it's turning into a more cogent campaign, we're having fun, loving the characters as they develop, and I want it to kick on.
 
Currently, the acolytes are aboard a Dauntless-class light cruiser they assisted in recovering from a space hulk after it was lost in the warp around 50 years previously. Their Interrogator saddled them with acting as "honour guard" for its return to a civilised planet for refitting in the service of the Holy Ordos. The fun is in the fact that the ship is virtually a wreck. It leaks atmosphere, is riddled with warp-tainted remnants of the previous crew, has no void shields or weapon systems and has a Gellar field that's "a bit rickety" (as their Tech-Priest put it). The Admech contingent who are actually running the ship have nothing but disdain for them; and as the ship used to belong to a very dodgy Rogue Trader, it's full of heretical and xenos artefacts (none of which the players understand and have had the good sense not to mess with).
 
The ship is a great setting - they've developed a bit of a love-hate relationship with it. I want to keep it around, but when they arrive at their end point, they'll have to hand it over. 
 
I had an idea to keep it - and this is where I need the opinion of my learned friends...
 
They are a fairly puritanical group. I'd thought maybe I could do a big reveal of their inquisitor as a radical who's stepped way over the mark. Over a series of adventures, they would learn this and have their loyalties tested. Finally, they would either join her as radicals (unlikely - they're pretty big on the "burn em all and let the Emperor sort em out" approach), or turn on her and reveal her to another Inquisitor, preventing her plot from all falling into place. 
 
This would leave the holy ordos in an embarrassing position - they can't really acknowledge that one of their own has fallen and they can't just execute the acolytes (who have significant influence by this stage). They decide to get them out of the picture by procuring them a ship and a Warrant of Trade. 
 
How magnanimous! But what shall our ship be...no...you can't mean...
 
The next stage of the campaign will be the characters saddled with no money, a ship that could be amazing, but barely works and has virtually no crew (in Rogue Trader terms - a broken ship and virtually no Profit Factor). They have to use all their wit and guile to just get the **** thing moving. 
 
Thoughts?