So while going for this after finishing everything else in the game, I found it tedious and slow. I played around with some setups and found an efficient way to boost this out while maximizing XP gain. All the other guides I've seen show ways to average 3,500 XP a match, but with my method, you can average 4,600 - 4,900 XP a match.
1. Load up Versus mode.
2. Select Incredible Hulk first, Spiderman Second for your characters.
3. For the opponent, choose Black Widow, and whoever else, the second secondary character doesn't matter.
4. Start the match.
5. Start with Hulk's Leftmost Launcher Super Attack, and then combo switch between the two characters doing the left most attacks until you reach the end of both character's super attacks. You want to do this in one Combo and it'll register as a 5 hit Ultra Tag Combo, resulting in huge bonuses of XP.
1. Hulk Left SA (Right Arm in Air, bring straight down),
2. Left hand up in air to switch to SpiderMan,
3. SpiderMan Left SA (Both arms out in T-shape, push towards middle), Tag Combo Hit #2
4. Left hand up in air to switch to Hulk,
5. Hulk Middle SA (Both arms out in T-shape, push towards middle), Super Tag Combo Hit #3
6. Left hand up in air to switch to SpiderMan,
7. SpiderMan Middle SA (Both arms over head, lift right leg), Ultra Tag Combo hit #4
8. SpiderMan Right SA (Right Arm in Air, bring straight down), Ultra Tag Combo Hit #5 :: Combo ends here.
9. Left hand up in air to switch to Hulk,
10. Hulk Right SA (Arms out to right side, swing like bat towards center)
11. Black Widow's HP is depleted, Round 2 or end match and retry.
See the Youtube video I've included to see this method in action.
In Round 1, I made a minor mistake, but Round 2 is the full combo in motion.
With this method, you can have both Rounds done in 20-30 seconds and then just use the controller's Down + A to skip through to retry. ~4,800 XP every 1-1:30 minutes with loadtimes.
The finer points on why this works:
1. If you do the Super Attack and it registers as "FAST" instead of "normal" or "slow," you get more points.
2. You really want to make sure you do this as a full combo to maximize your points.
3. I chose Hulk and Spiderman because with my experience, their Super Attacks were easy and similar to each other, so there wasn't much confusion on where to move to get it to trigger. Also with my room's lighting, my Kinect was most consistent tracking these moves.
4. We choose Black Widow as the opponent for this match because she has the least amount of HP in the game.
5. After you finish the Ultra Tag Combo with SpiderMan, you want to switch back to Hulk and finish Black Widow off with him so you can immediately start off Round 2 as Hulk and start the process over again.
The total XP required to hit Immortal Status is 550,000 XP. It's Rank 20 Gold. Don't know why the name of the achievement is Legend, as that's rank 19.
4,600 - 4,900 XP / 1 minute = Awesome.
It's recommended this be the last achievement you do other than the Trials/Challenges as those don't add to your XP. You do gain XP in Arcade, Versus, and Campaign.
If you have any questions or comments, please feel free to message me and I'll clarify anything that needs to be.
UPDATE from comments:
- I've found a better character combo. I use hulk and magneto as their moves are the same motions for all of them and I average about 5,100 xp per fight in the same amount of time as your combo. It's up to you if you want to add this to your solution Posted by chaotikilla on 29 May 13 11:36:34