[GSM]

Well, since you stated it was bland, for starters the abilities for the class could be a False Arm canon, repeater bow, throwing knives, and throwing bombs, plus great sword related attacks & most important a Berserker armor or buff related ability; as for unlocking the class it could be done where you're branded and have to survive an eclipse https://youtu.be/5O8vsjsMelc?t=6439 :^)

The branding from the Eclipse is awfully similar to going into a Dark Zone, so they'd be a Shaitan, if not a tragic character background.
Throwing knives could be flavored as that one Spellthief attack, and the false arm cannon could be a stolen Fir or Explosion attack, given its explosive abilities.
Repeater bow is kind of falling apart, but I'd probably say this would be a Poison Dart from the detective gear from Air (bear with me, buddy).
Throwing bombs is just the item, or again, stolen Explosion.
Greatsword attacks could be used with Ghost, especially with a Ether Invitation slung around and how intimidating Guts is in the Berserk series. Plus, this lets him dodge, parry, and riposte attacks in quick succession.
Finally, the Berserker Armor buff could be either a gradual effect from Ghost's stat bonuses for missing HP, as well as reflavoring Last Chance to having his wounds rearranged (coincidentally, this also works with Painproof and Wraithguard). That, or even a stolen Death Knighting (+10 to all stats but Vit is incredibly useful). It also gives time for an entire paragraph of the transformation into the Berserk state from the armor.
Maybe a little something extra could be the raining blood ability from Ghost being shot from the brand on the back of his neck. Just flavor it as such, and you'll be good.

EDIT: Gigantys or any Dragon Remains/Huge Blade weapon could also suffice for a greatsword, given its range. Giant blade Gigantys could hit from 3 tiles away, and it could hit hard. Dragon King's Armor, Two Hand, and heavy investment in defenses/skill/definitely Strength.

TL;DR: We don't need a class for this, you can make it all by imagination. Just don't hurt me.