The SMB team has said on Twitter that it counts a sum of the best play times in Hell.
From the Super Meat Boy Forums:
You must clear Hell, both light and dark world
The sum of your best times in Hell must be less than some threshold
Apparently, the threshold is 500 seconds.
As usual in Serious Sam 3, the area in question is in serious plain sight. Acute players will have noticed this small green blinking item in The Power of The Underworld, roughly 400 kills into this serious level (after the serious infinite rocket storage).
It's seriously right under the crosshair. But how the hell would you get up there?
Climb on this seriously damaged wall further ahead, opposite the construction area leading to the next serious part of the map.
From there you'll see serious "secret keys" blinking in serious purple. Go back to the where that green item is located - the serious gates will now open for you.
You'll find a seriously long ladder on your left, before heading through the second gate. Climb it up, and, sure enough...
It's no crash to desktop, but it's a serious sight to behold, plus you get to have a peek on the following serious area. A very good peek I might add, since the green blinking item just around the corner is a serious sniper rifle. Unfortunately, it only comes with 5 serious shots and it appears it only can hold 10 anyway.
Remember to take the ladders on your way down, or you'll simply crash under your serious weight and suffer a seriously humiliating death. You can simply start taking the stairs with E, then jump off them and press E just before reaching the ground serious fast.
Best Answer
Edit: I have found a better song to get this achievement with -- better, because it comes with Beat Hazard itself.
The track is "Beast Mode" by xKore, and is located in your beat hazard folder.
While Badp's answer works for the folks with BOSS RUSH, those folks who want to stick to just the base game of Beat Hazard are in luck: the same pair of boss ships can spawn in normal mode, and on normal difficulty, in a base game without any DLC whatsoever.
It may take a bit of parsing through your library until you find a song with both a "pair boss" spawn and enough time / lack of danger to kite them safely for 1 minute, but it's not outside the realm of possibility. To the best of my knowledge, it is okay to die after stripping both bosses, doing so won't invalidate the achievement (though you do want to make sure that it's not your last life).
In my case, I happened to have Dragonforce's Valley of the Damned handy, which features enough guitar power shredding to keep your guns nice and perky for most of the song. Disciples of Babylon was the song that ultimately got me the achievement, though, like most Dragonforce songs, it is a little on the long side.
The point to take away from this is that it's totally possible to earn this achievement in normal gameplay - experiment with your library, you might find an even better song!