add MO_TRIPLEATTACK 'nk' with 0x40 - Skill ignores target's flee (magic type always ignores)
263,-1,8,0,-1,0x40,0,10,-3,no,0,0,0,weapon,0,0x0, MO_TRIPLEATTACK,Raging Trifecta Blow
or if it doesn't work.
I think you can add new line here src/map/battle.c#L2148
if (skill_id == MO_TRIPLEATTACK) return true