Death or Glory (Combat)
Even when facing a larger foe, you aren't afraid to take great risks in order to finish the fight.
Prerequisites: Str 13, Power Attack, base attack bonus +6.
Benefit: Against a creature of size Large or larger, you can make a single melee attack as a full-round action, gaining a +4 bonus on the attack roll, damage roll, and critical confirmation roll. You gain an additional +1 on this bonus at base attack bonus +11, +16, and +20 (for a maximum of +7 at base attack +20). After you resolve your attack, the opponent you attack can spend an immediate action to make a single melee attack against you with the same bonuses.
Special: You can combine the full-round action attack this feat allows with the benefit of Vital Strike, Improved Vital Strike, or Greater Vital Strike.
Ok so, if you attack a creature with a reach weapon using this feat, and enlarged person via spell/potion/whatever you get 20 feet reach if I'm not mistaken (add 5 from lunge if they can be used together) that means you have a good chance of getting away with +4 attack/damage with 1 feat (and provided the target is large+) without the risks!
I wonder if this combo turns death or glory from a horrible feat to a great one? (Not to mention making the vital strike chain look more appealing)
Nope. I wouldn't even call it "situationally useful." The problem is, you are using a full-attack to make one strike, and it requires a BaB of at least +6. Which means you are giving up your iterative attack for it.
Even ignoring haste or similar effects, it is extremely unlikely that +4 to attack and damage is going to get even close to the average damage of a second attack. That you need to go to quite a bit of work to set this combination up just makes it worse.