The goal is to build an incentive system where "I'm going to farm for a while" yields less XP than "we're all going to advance the adventure together". That way, adventuring together is the most effective way to get more powerful.
Step one, disincentivize solo farming. Every build has a counter. He's stealthy? Monster with blindsight. Wizard with alarm's throughout the area. Divinations. The ultimate sentry, who put so much into perception and investigation, and has a background of Sentry (you'll have to make that background) that, within their limited area of expertise, they are a god; they have clear-cut the area, burned the undergrowth to the ground, and hid 1,000 pit traps around their camp.
Know what's really boring/doesn't give you a lot of XP? When you fall in a pit and break your leg, and have to wait for your party to rescue you (accumulating XP as they go).
Immobilization traps can be great for this. They won't straight up kill him, but the humiliation of being repeatedly rescued by the rest of the party (who are accumulating XP in the process) should very quickly wear him down.
Adventurers form parties because adventuring is dangerous. If this guy is able to cut a swath through your encounters solo, it's because you need to up the challenge of those encounters.
On top of that, life doesn't stop for the rest of the party while he's gallivanting around. Maybe they stumble across some treasure. Or get ambushed. If they get ambushed by something that would have been really useful to have that rogue to face and they waste a lot of resources unnecessarily, then the others will start pushing the problem player to stick with the group.
Every time he says he's going off on his own, I'd say, "Okay, you go scout through the forest, yadda yadda yadda, we'll come back to that. Everyone else..." Anyone who aggressively steals the spotlight should be delayed before they get that spotlight.
Personally, I don't like messing with the XP system too much (as others are suggesting). By and large in my games, people in a fight get XP, even if, really, the fighter just cut through everything. You get the same XP for avoiding a fight (stealth should not get penalized). You get half XP for being forced to retreat from a fight (you didn't win, but you did learn something). There are also story rewards: you found the lost treasure of [whatever], rescued the mayor, whatever. Finally, every player gets "bonus" XP for being particularly effective at a crucial moment, roleplaying well, overcoming a personal challenge or weakness, or, and this one's key, increasing party cohesion.
Finally, the carrot: build encounters around this guy. He wants to stealth around? Have him scout along a cliff, taking out archers that are threatening the group below. Everyone else is engaged in their own combat encounter with [insert whatever], everyone's on the same initiative, everyone's playing, everyone's getting XP. And make it clear he's getting more XP than he would on his own, since he's getting XP for the rest of the party's combat encounter (since this is really all just one combat encounter).
The only real problem I could see with a guy like this: he doesn't just want to be powerful, he wants to be more powerful than the other PCs. If that's the case, you're going to have to have a carefully worded talk with him. And if he's still a problem... you can either kill him until he gets the idea (and institute XP penalties for death, either on resurrection or on new character creation), or kick him out of the group.