In all honesty, the only two people in the world who can possibly guard him one-on-one in a game situation are LeBron himself and the refs.
1) I know LeBron is brimming with confidence since winning his first championship, but he still suffers from bouts of self-doubt or complacency, where he doesn't attack the basket and settles for long jumpers. When he falls into bouts of this, he is technically guarding himself and helping out his opponents.
2) The refs can easily affect LeBron's game. LeBron's best move is to attack the basket like a bull, drawing contact on every defender in his way. A large percentage of these are offensive fouls that are never called. If the refs ever called these, they could affect LeBron's potency. Remember when he fouled out of Game 4 of the ECF last season? FOUR of his six fouls were offensive fouls. Let me repeat that: FOUR of his six fouls were offensive fouls! If these were called fairly and honestly every game, LeBron would have a very difficult time being as dominant as he is (same goes for Blake Griffin).
But, we all know how the NBA is, and I highly doubt LeBron will ever again foul out of a playoff game.
So, when it comes to actual opponents guarding him, well, obviously a "team-oriented" scheme is best, but if you're looking for individual defenders who can contain LeBron one-on-one:
- There isn't a better tag-team in the league than Pierce and Green. Problem is that when Pierce expends too much energy guarding LeBron, his offense suffers (especially over a 7-game series). So, Green is actually the key for Boston.
- The Thunder have a good trio to throw at him in Durant, Thabo, and Ibaka, but none of them can contain him for long.
- The best of the rest: Kobe, Iguadola, Pietrus, Allen.
You need to have length, but also a bit of bulk. You need to have speed, but great body control. You need to have good balance and be smart enough not to bite on fakes. You need to stay in front of him and contest his jumpers by going straight up. If he goes to his left, he's driving. If he goes to his right, he's pulling up for a jumper.
And, even with perfect defense, it always comes down to the refs blowing their whistles, which they tend to do more often than not for LeBron's sake.
Remember how good Pietrus was on LeBron last year? He stayed low, didn't bite on fakes, and contested shots by jumping straight up... and he was still whistled time and time again... it's a refs' league.