Alright... i think I can help you with this...
Keep in mind, I played on the Xbox, so I'm not sure how well my tips will be applicable on the PC:
1) on ultimate badass, friendly fire killed me faster than anything else. At first, I assumed it was the alien warriors, but after a few attempts I realized oneal was hurting me while no aliens were near me. So stick to the sides out of the crossfire.
2) when the raven (big boss alien) is stunned and/or distracted by your teammates, take a few seconds to whack a few of the smaller aliens crowding you. This will temporarily relieve you from that threat, and stop oneal's dumbass from shooting you in the back.
3) focus on the timing of your swings. Don't just button mash, or else the raven will counter you with that headbutt move.
4) try to corner and trap the raven and just let loose on him. If you're really lucky, he'll get glitched and stuck in the wall.
5) never hop out of the power loader, no matter how tempting that health pack is.
6) lastly, I read on another forum that when gearbox released a patch a while back, one of the 'fixes' was to double the raven's health. So it takes twice as many hits to kill it. Consequently, it'll also take twice as long which made the achievement for defeating the raven under a specified time limit impossible. I had to clear my Xbox of the updates, disconnect from the Internet, and play offline in order to get that achievement. Then redownload the patch once I hooked back up to the internet. It worked for killing the raven faster and getting that achievement. If it's possible for you to delete that patch and play on your PC, that might be worth a shot... But be warned, that patch fixes a LOT of glitches, which will make many other parts of the game very frustrating.
