Using the wrong units.

Mines are physical wall Valter, Bladetome Tharja or CD 6 Joshua

I basically build my soren as a magic alm, due to him having watersweep
so, that's my answer

I've got a Hawkeye with several builds that I adjust from time to time. One fun build that isn't very good is this one:

Hawkeye, +atk -spd.
Weapon: brave axe+
Assist: Drag back
Special: Galeforce
A: Death Blow 3
B: Desperation 3
C: Threaten Def 3
S: Brash Assault 3

He's got 5 merges and his speed stat is still only 16. So he gets hit hard (but usually survives), then cleans the field in the next turn. Honestly, he's much better off using a different kit, but whatever.

P.S. Just ran into a Linde that had her speed boosted to 49 in arena (literally more than triple hawkeye's speed stat) so I came back to add this note: It is really satisfying to run into fast units, and know that their 49 speed is just as good as a 21 speed. So much wasted potential.

I'm actually thinking of running this on Lon'Qu, I just need a +Atk or +Spd, and I'm thinking of a special for him.

*Regrets using Lon'Qu as Vantage Fodder*

My Brave Axe Freddy. Because Cherche does it better.( not the best example, but its about the only one i have.)

When his weapon finally gets refined, they'll all be sorry.

Using Zephiel in general on my armor team.

Don't know about the "someone else can do it better" angle because it's based on a unique skill but ...
I suppose my Drain Tank Ephraim.

Accidentally double posted >.>