Rollerdrome

This is easiest with assists on (infinite ammo and invincibility)
Wait until you have all the weapons. Before starting a trick off the (i think they are called half pipes?) make sure you equip the explosive. Then on any given level you will do a front flip with any combination of 2 directions on the dpad for your X hold for the special grabs EX. Left Left X. Do not let go of X and just keep spinning (hold left or right on the left analog while holding the X button. You Will be spamming explosives on the ground to keep yourself afloat and drastically increase your single move score. Make sure to use the slow mo ability to kill enemies (switch weapons if need be but dont forget to switch back to the explosive) only do this when the combo is running low. after you get a decently high score from the single grab (around 50 or 60k if you are doing the last level) try to increase the multiplier as high as you can and do some other side tricks to rack up more points along the way (or just aim for 100k from the one grab and hit a multiplier of 30) it seems daunting but its very easy to do with some practice.

In my video at 6:45 I show an easy way to get a high score

Achievement Guide:

In my video at 6:45 I show an easy way to get a high score

Achievement Guide:

As BiLLzuMaNaTi has already mentioned there is currently a cheese method to help get that 3 million combo, however if that method is to ever be patched I have some tips and tricks that I have covered in my video at 3:51 for those who prefer a written guide I have included that as well:

Cheese method:

1. To do this you'll first want to earn a decent multiplier, I went for 25.
2. Then equip your grenade launcher.
3. Perform a unique trick while spinning.
4. Then before you land keep shooting the grenade launcher with the right trigger, as well as holding the left stick to the left or right to continue spinning.
5. You'll want to do this in a closed area so you end up against a wall.
6. Then aim for a score of higher than 120,000 as 25 x 120,000 is 3 million.
7. Make sure you don't go over the elapsed time in the top right-hand corner otherwise you'll be deducted points.

Highscore legit tips and tricks:

1. Aim to complete the round in a single combo, you can increase your combo by killing or damaging players and collecting combo tokens. Performing tricks will only increase your score not the multiplier.
2. Only increase your combo when the multiplier is about to run out, this will extend your combo for as long as possible allowing you to perform tricks inbetween each multiplier.
3. You want to aim to perform every grab trick when going for the high score, you'll be netted more points for performing unique tricks rather than the same trick over and over again.
4. Always flip and spin when performing these tricks, you'll rack up a lot more points flipping and spinning when performing the grab trick.
5. Don't dodge anything. Dodge cancels your tricks and doesn't increase your score or mulitplier. And because we have Invincibility turned on we won't take any damage or lose our combo when we are hit.
6. Don't take your eyes off the multiplier. You'll want to constantly look at the multiplier, so you know when to kill the next player or collect your next combo token, with that in mind, always have the next enemy or combo token close by.