OK, so let's work this out.
A creature that starts with a 0 ATK hits for 3 with it's 1st attack. This implies that Overdrive takes effect before Adrenaline does.
So, the cycle goes like this:
1) A 0-power Adrenaline Overpower creature attacks.
2) Overdrive kicks in and raises the creature's ATK by 3 and reduces it's HP by one.
3) Adrenaline checks to see whether or not another attack is warranted. It is, so a flag goes up. "Extra Attack incoming!"
4) Adrenaline checks to see how it should modify the damage dealt by the creature on this attack. Since this is the first attack, the modifier is always -0 damage.
4) Damage is dealt.
5) If the creature now has 0HP, it dies.
6) Next turn, the 3-power Adrenaline Overpower creature attacks again.
7) Overdrive kicks in, raising the creature's ATK to 6 and reducing it's HP by one.
8 ) Adrenaline checks to see whether or not another attack is warranted. At 6 damage, 3 attacks are the norm, so one more attack is in fact warranted. The "Extra Attack" flag goes up.
9) Adrenaline checks to see about the damage modifier for this attack. For a 6-damage attack, the usual modifier is -2 for the second attack, so a -2 damage modifier is applied to this attack.
10) Damage is dealt.
11) If the creature now has 0 HP, it dies.
12) Next turn, the 6-power Adrenaline Overpower creature attacks again.
13) Overdrive kicks in, raising the creature's ATK to 9 and reducing it's HP by one.
14) Adrenaline checks for an extra attack. At 9 damage, two attacks is normal, and this is the third attack, so no more attacks are warranted.
15) Adrenaline checks to see about the damage modifier for this attack. For a 9-damage attack, there is no normal damage modifier For whatever reason, when there is no damage modifier, the damage is set to -3 regardless of other circumstances.
16) Damage is dealt.
17 ) If the creature now has 0 HP, it dies.
To correct the bug in the most simple manner possible, swap the order in which Adrenaline and Overdrive do their checks. If Adrenaline checks before Overdrive, a 0-attack creature will attack at 3/6/5, a 1-attack creature will attack at 4/5/6, a 2-attack creature will attack at 5/6/7, and so on.
