In the original KR, Abomonation's death explosion deals 250 True Damage. But that is not the case in KRF.
The amount of damage differs in relation to armor rating, but not completely.
no armor: Ashbite, Bonehart, Mirage, etc. - 250 damage
20% armor: Assassins with star upgrades (220HP) - get slaughtered.
35% armor: 206 damage - Karkinos
40% armor: 200 damage - Assassins with star upgrades + Dieredre's Wings of Light, Templars without star upgrade, Level 1 Death Rider, Kahz, Sha'tra
45% armor: 193 damage - Saitam
50% armor: 187 damage - Templars with Defensive Stance upgrade (+10% armor), Level 2 Death Rider, Grawl
60% armor: 175 damage - Templars with Defensive Stance and Veteran Squad upgrades (+20% armor), Level 3 Death Rider
65% armor: 168 damage - Alric
70% armor: 162 damage - Lucrezia
75% armor: 156 damage - Dierdre
80% armor: 150 damage - Templar with star upgrades (60%) + Dieredre's Wings of Light
90% armor: 137 damage - Lucrezia + Dieredre's Wings of Light
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For every 10% armor increase, damage is reduced by 12-13.
It seems like the KRF Abomination's death explosion ignores half of the armor.
Thus, the formula for its damge is 250*(1- armor rating÷2).
For example, take Alric: 250*(1-0.65÷2)=168.75
Another example, Saitam: 250*(1-0.45÷2)=193.75
See?