So I got luck and got 2 L!Hector (+Def -Hp and +Spd -Def) and I don't know wether I should merge him or fodder him for vengeful fighter.
+1 HP/+1 ATK is whatever, Distant Counter or Vengeful Fighter on some unit you're trying to build is much nicer. I would just hold him in my barracks if you're not sure whether you're going to merge, maybe you pull a bunch more copies on his next legendary banner and want to go for +10 in which case you can rely on regular Hectors for DC and M Grima for Vengeful Fighter.
L!Hector is definitely an great long-term project; he has amazing stats, skills and is currently the only Legendary armoured unit. I recommend merging unless you desperately want vengeful fighter on another one of your amoured units.
Do note however, that if you merge into the +def -hp Hector he will get +1hp/+1def on the merge as his def will be higher than his attack.
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