Solution is now updated and includes the best method for the Legendary Edition update + Patch 1.19! The video below to go with the solution was made during Patch 1.05 but it still works.
First off DLC characters aren't required (Darkseid, Red Hood, etc.). Second, you're gonna have to complete Story mode in order to unlock Brainiac as you need him Lv 20 as well for this achievement. So go ahead and do that first. You'll also earn a tiny bit of Xp for your characters from Story mode even though the game doesn't show you earning Xp for Story mode fights. Everyone you play in the Story will be around level 3-4 once you complete it. Third, go ahead and complete everyone's arcade ending for that achievement as well to level them up just a bit further and make it easier on yourself for time.
You need a total of
61'078 character Xp to reach level 20. You earn more Xp based on:
-Time Left on the clock
-Damage Taken
-Enemy Level
Feel free to check the Xp requirements for each level:
*** Spoiler - click to reveal ***Lv 1 - 2000
Lv 2 - 2100
Lv 3 - 2205
Lv 4 - 2315
Lv 5 - 2431
Lv 6 - 2552
Lv 7 - 2681
Lv 8 - 2814
Lv 9 - 2955
Lv 10 - 3102
Lv 11 - 3258
Lv 12 - 3421
Lv 13 - 3591
Lv 14 - 3772
Lv 15 - 3960
Lv 16 - 4157
Lv 17 - 4366
Lv 18 - 4584
Lv 19 - 4814
Fastest Method2 Player Local Versus (Updated version!)
-Set the
Round Timer to 300 seconds in Gameplay Options
-Load up a 2 Player Local Versus Match (Multiplayer -> Versus)
-
Sign in a second profile. This profile MUST have at least one
Lv 20 character on it!*
-If you don't have a Lv 20 character, read below...
-Profile 2 selects the Lv 20 character as the opponent. Make sure it's gearless.
-(Optional) Gear up your character on your main profile, specializing in the STRENGTH stat
-In Match Options, turn
Level Handicap ON.
-
Turn Arena Transitions offThis method happens to be just as fast as pre-patch. You get
1300+ XP per match. Once your character reaches level 16, you'll start earning 1000 XP per match which is the same amount as it was pre-patch. Using this method will take you
about 40min to go from Lv 1-20 though it could be faster depending on how you do. At 40min a character it will take you
roughly 18.5 hours for the whole cast.
Beat up the second profile as fast as you can getting Flawless wins. An easy way to do this for no effort is to do a 2 hit combo using Wall Bounces (back + Heavy) and/or Ground Bounces (forward + Heavy). If you Meter Burn the Ground Bounce/Wall Bounce, it’ll do more damage. ALSO, if your character has a trait that increases their damage (Superman & Bane are perfect examples) then use them!!
NEW: NEW LEVEL 30 LEGENDARY EDITION UPDATEAs of the Legendary Edition update the level cap has increased from 20-30. This means that you can now boost your levels even faster by fighting a level 30 opponent. Do the same strategy as above, fighting against a second profile that has a character that's Lv 30. This will
decrease your completion time by roughly 10min a character from levels 1-20, meaning you'll be looking at around 13.5 hours for the whole cast. That's a huge difference!
Some gear have Augments which can help you earn more XP:
-Expertise (Earn More Character XP per match)
-Pure Focus (Earn More Profile/Character XP per match)
*Question: What if I don’t have a Lv 20/30 character to use to help me level up??The best workaround to this is to level up each profile’s characters together. What this means is if you are levelling up Superman (for example) from Lv 20 and your second profile also doesn’t have a high level character to boost from, then you must level up the characters together. So, it’ll work like this:
-Profile 1 (you) will level up 4 times
-Profile 2 (second profile) will then level up 4 times.
This is because every 4 character levels or so in difference results in an XP dropoff. You earn more XP for fighting characters of an equal level or higher level than your own characters. If your opponent is 4 character levels below you, you’ll earn less XP. This effect is more noticeable when fighting opponents of a great difference in level.
If you have a second profile that has a Lv 20 character on it (like me) starting from the Legendary Edition update, then use that. I’ve been levelling up a character on my main profile 4 levels, then my second profile the next 4 levels, and so on until Lv 30...
It should also be noted that fighting against a Lv 1 character that is ‘Equalized’ to Lv 20 via the ‘Level Handicap’ match option is not the same! The Level Handicap option is only there for competitive reasons to equalize stats, not XP. So, in sum, you have to fight against opponents that have a similar/higher character level going into the fight for more XP, not one that is manipulated using Level Handicap. You should use the Level Handicap option only if you’re fighting someone stronger (A Lv 16 vs a Lv 30 is not going to be effective… the Level Handicap brings their
stats to an equal playing field!).
I highly recommend levelling the second profile to level 30 (takes a little over 2 hours from scratch) as this will save you a lot of time in the long run.
AlternativeSingle Player Fights vs AI (Updated version!)
-Set the
Round Timer to 300 seconds in the Gameplay Options menu
-Load up Single Player Fight vs AI
-Select the character you want to level up
-When choosing the CPU, press Y to bring up the options and
set the CPU level to level 30-In Match Options, turn
Level Handicap ONDoing this method nets you anywhere from 500 - 1200 XP depending on how fast you win and how much damage you take. I recommend fighting against a character that is fairly easy to rushdown/is slow.
Another Alternative MethodOnline Private Versus 1v1:
-
Competitive Mode OFF. Throw on all your gear and have your partner stay gearless.
-Turn
Level Handicap OFF. This will make it so you stay a high level and your partner stays a low level. If your partner doesn't have a low level character, leave it ON otherwise you're going to be wasting time beating up a high level character.
-Turn Arena Transitions OFF (Optional but transitions do take a while which wastes time).
You get 920+XP each flawless win on your partner in these matches. For easy purposes, hit your opponent with a Ground Bounce (forward + Heavy) twice for a two hit combo. If you can't land two of those in a combo, hit the opponent with a Wall Bounce (back + Heavy) then a Ground bounce. If you Meter Burn the Ground Bounce or Wall Bounce, they'll do more damage. Also if your character has a special move/trait to increase their damage, use it to make it go faster (Bane and Superman are great examples).
Last ResortYour next best alternative is doing Endless mode in the Battle Simulator located in the Multiverse. Set up an AI loadout and have it do the Endless run for you. I’ve never seen the AI earn less than 300 XP per win in over 100 fights. They mostly earn over 500 XP every match and can earn up to over 900 XP. Of course if you do choose to play it yourself there is the chance you can earn more XP but you must know what you’re doing and the fights will get progressively harder for you to beat, whereas the AI can manage these fights much better.
Final NotesAI Battle Simulator is not nearly as effective as you'd think even if you sim games at 4x speed. Wins only net you 180-390 Xp per match depending on how good your AI does and you're not guaranteed to win every time. If your AI loses you only get 40-60 Xp which is horrendous. On top of this you have to reload the sim, re-kit your characters with gear and set up their skill points, etc. which wastes more time. The 4x sim speed simply doesn't make up for the Xp payout and time spent setting up/going through the sim.
Happy grinding!
-Credit to Ian Cole for telling me about the updated 2 player local versus method.
-Credit to PJGameFreak for telling me about the updated Single Player Fights vs AI method.
-Credit to Rapture639 for help testing Online 1v1 Private match XP payouts.