Str 5 12
Dex 15 20
Int 11 13
Con 9 11
speed 8 11
per 6 8

single handed 3 6
Tenebrium 1 2
Two handed 0 1

Armor Specialist 0 1
body building 2 4
shield specialist 3 4
willpower 1 3

expert marksman 1
Scoundrel 5
witchcraft 5

Charisma 1
Leadership 2 4
lucky charm 1 3

loremaster 3 6
lucky charm 1 3

lockpicking 1 2
pickpocketing 1 3
sneaking 1 7

All skilled up
back stabber
bigger and better
pet pal
swift footed

The first column is base stats, the second number following it is stats after Traits and gear is figured in. While playing I did not really take traits into account when doing my dialogue, I just played "the good guy" and that gave me sufficiently pleasing buffs and stats.

This rogue has:

Level 21

Damage 191-284
Armor rating 117
Blocking 77%
Critical Chance 18%
Offense Rating 169
Defense Rating 159

HP 2304
AP (max 19) (start 11) (turn 9)

fire 190%
water 125%
earth 145%
air 195%
tenebrium 20%
poison 85%

sight 28.20
hearing 13.00
movement 5.90
initiative 20

The only skills I have on skill bar a all are
Tactical retreat
Daggers Drawn
Death Punch
Walk in Shadows
oath of desecration
Death Knight Bane
Summon Armored Undead Decapitator

Those are the only skills I used at late game and no other skills.

Effects from gear and Traits:
Immunity to slipping
Allows you to cast Iceshard(never used on this character)
Inflict poison on contact
Immune to curse
Immune to fear
Immune to Charm

My favorite combo is:

Turn one: Stealth and go behind the toughest enemy in battle, end turn
Turn two: Go behind that enemy again because by now it has moved, end turn
Turn three: Move to behind the enemy again because he has moved, Oath of desecration, daggers drawn(backstab bonus), end turn
Turn four: Move behind enemy again, Death Punch, attack(backstab bonus)until I run out of AP, this killed everything in the game except for the final two bosses.

To top that off, I also used this character to do everything, he was my "main character" the other one was just there for a free ride and to give me extra stats from traits from dialogues.

In the end, this guy was very lethal and was impossible to hurt with anything but status effects. Not even lava could hurt me, in fact it healed me. I was always nuking my rogue along with the enemies, didn't bother using heal skills because Friend and foe alike were always healing him with their attacks.

In the end, he was the absolutely most useful character I had, he did tons of damage and was a defensive monster at the same time, in that he would soak up damage but never actually get hit.

There is no way that I built the best rogue possible. In the right hands(not mine I am sure) this very same build could be optimized to be even better than it is, so as overpowered as it was for me, if someone who was better than I was was in control of it, it could have been better.

There is no such thing as underpowered in this game, everything is overpowered, all of your characters are overpowered no matter what, it comes down to just building the right character for you.

I mean, even as far as stats goes, you are not limited to just what you get when you level up, once you unlock the secret keeper in your homestead, every time you level up she has two new books available for you, then add to that the fact there is no level cap, I could have conceivably pushed my characters up to level 23(there were things I did not do, i did do most of everything though), during the last boss fight, after I killed the first boss, all my characters hit level 22.