The most OP Brave Frontier unit I can think of

Toad1 back and stressed! anyway, here's what I made!

Five Heavenly Lights, Ardnell (Light) (Genderless)

Leader Skill: Holy White Flame of the Creator
All units gets a 90% boost on all parameters & BB Gauge fills up greatly every turn

Brave Burst: Shining Blade
2 Hit AOE Powerful Fire, Water, Earth, Thunder and Light attack with high chance of paralyze & poison

SBB: Termination Mode: Full Charge Holy Blade
130 hit AOE Powerful Fire, Water, Earth, Thunder and Light attack with high chance of paralyze & poison

Lord Stats: 9250 HP
                 4538 ATK
                 2000 DEF
                 4000 REC