Soulcalibur IV

It takes roughly 50-60 wins to reach level 20. It goes way faster if your boosting partner has full experience, as you gain an extra 50 per win. I suggest fisrt attack and ring out on a full EXP partner. You get 148-168 EXP a win depending on how many rounds you won. It takes 3 wins for a level.
Also izret102 found these
Just some extra info the Win count might vary. I boosted these myself with 2 consoles/copies of the game.
Win - 80 (varies based on other factors?)
Lose - 0
First Strike - 3
Perfect - 10
Critical Finish - 7 (Cancels Perfect)
K.O. - 5 (Non perfect win)
Ring out - 3 (Cancels Perfect)

(Boosting Method):
Ok, just got this with my buddy. You're going to want to pick Shura, and then pick a map where you can easily ring out, we did the River one where you're on a small platform going down stream (yes, I forgot the name). Then start up the game (be sure it's a ranked match) and run at your buddy and push him to the edge the while sprinting at him and he's near the edge, press Y, or Y+B and you'll do an Animation Grab on him and throw him off the edge...

Average Round Time: 4.5 Seconds.
Average Match Time: Under 30 Seconds (Damn Cut Scenes.)

Do this method and you'll have this (and the 100 Online Games) in the bag.

In order to get to level 20, it takes exactly 65 wins (no losses) against a level 1.

From levels 1-10 or 12ish, you can get 139 pts per match (Win = 100, 3x Perfect = 30, 3x First Attack = 9). That is doing a Perfect round without a Ring Out (Ring Outs negate the points from a Perfect). That translates to 3 or 4 matches per level up to that point. 2 or 3 matches to get to the full exp for that level, then another match to hit you to the next level. When you level up, you should be halfway to the next level.

Once you reach level 10 or 12ish, your points per win go down to 119 per win, due to fighting someone well below your current level. You get 80 pts for the Win rather than 100.

Like Rogotogo, I used two copies of the game + two consoles to do it myself. It takes a few hours to do and is quite boring.

Also, you do NOT get experience points by doing Player Matches. These all have to be done in Ranked play.

you can also edit a character and take away all his/her equiptment - for example a naked lizardman only takes 3-4 hits to KO and roughly 3-4seconds per round

I boosted it yesterday.
When you levelup , you start new level with 250/500 points.

As stated, if you have 499/500, you need 2 wins to levelup, as the first win will bring you to 500/500, the second will give you a levelup.

Ringout win is totally faster but gives less points (118)

HP win is slower but gives more points (138)

Fastest levelup combination is:

- Cervantes ringout win (run toward enemy and at border "Y" (x3 rounds))

- Astaroth HP win (down backward , X , Y (x3 rounds))

you reach 500/500

- Cervantes ringout

LEVELUP

If you win only by ringout you'll need 4 matches to levelup
If you win only by HP you waste more time/points

For those of you who don't have an "extra console" just laying around or simply want to play the online matches as they were meant to be played, I would say you're shooting for somewhere between 65-80 wins in total. Personally, I had a ~40% win rate, which I think is a tick below average, and ended up getting the achievement at 73 wins.

The tricky part is that as you get to higher levels, you can lose a substantial amount of exp points if you lose the round...and there are some folks who have clearly been playing online for a loooong time so you're probably going to get smacked around a bit while you do this. Plus, you can't just "back in" to a level up, you have to win while you have full experience for your _current_ level. For example, if you're at level 15 with 500/500 EXP and you lose all three rounds, you'll probably see a decrease of ~20 points after the round, bringing you to 480/500. Now, you have to get not just one extra win, but two...the first to get back to full 500/500 EXP and the next win to actually advance to level 16. Obviously, this requires you to win extra rounds over the long haul if you lose at full EXP, so make sure to bring out your A-game when you're about to level up.

The online matches still seem to be going pretty strong and there's plenty of opportunity to get this achievement before SC5 comes out, so get your Kilik-spam going and get that cheevo! Good luck!