User blog comment:Magna.Zero/Thoughts of this new event/@comment-36.71.186.194-20140715144537/@comment-24472911-20140718210703

Things like elemental buildings and unit bonuses can increase bonus attack quite a bit. My maxed Yuki Onna has 19999 (+11399) attack because of a level 5 (ish) elemental building, unit bonuses and an upgrade potion. That can occasionally OHKO Vepar and always does for Thrones (at full HP), but I generally rely on her procing instead.

tl;dr attack is different for everyone