re: defeating Starkiller
The others already pointed you to the base.
The best way to beat Starkiller is with melee weapons. Before talking with Ajurr to start the match, equip your character with the Proto Vibroblade, and Mission's Vibroblade if you have the 2 weapon feat, the strenght gaunlets and Brejik's Belt if you have it. Use all items that give you a high melee attack. Then turn on your force shield and take the adrenal strength, adrenal stamina, adrenal alacarity, and Battle stimulant. Your character should have 4 arrows pointing up on their portrait and a glow around them. Talk to Ajurr and start the match.
When the match starts, before you initiate combat, make sure your supplies are set to Medpack. Choose Attack before initiating combat. If you choose a melee attack immediately, Brenak's grenade attack misses and he'll take a shot at you while your charging, but your shield will limit damage. Now do your best to beat him up close and personal. Watch your health! If it gets low, use a medpack because Starkiller can deal 40 points of damage with one jumping blow. It only took this strategy twice to work once I used the adrenals and shield before entering.