Killer!Sans' AU takes place in a Genocide route, where Sans joins Chara on their Genocide (which includes killing his own Brother). There are 5 interpretations of these timelines:


#1: He killed Chara and continued on his Genocide.


#2: He joined Chara and made a partnered Genocide.


#3: He joined Chara in his Genocide, but later decided to kill them and continue his Genocide route.


#4: He is forced to do a Genocide run by Chara.


#5: Classic Sans brings back Killer's emotion and he stops his Genocide...


(Note: #3 is the most common route)

Profile

Appearance

He looks much like Classic Sans, but with a red target-like soul displaying, and liquid hate pouring out of his eyes.

Alternate/Underverse appearance

(Most likely to stand out from other Sanses) Killer's alternate
attire has him wearing the Sans classic striped shorts and sweater but
with an inverted color scheme, he still has his target-like soul. His
hoodie is a darker to classic Sans, with ruffled black colored fur
around the hood, at the bottom of the hoodie is a sort of trim with a
darker black, (the hood itself is also the same darker black) on the left
side of his hoodie is a black stain (either his blood/liquid hatred or
something else). His shorts are white with red stripes and he wears
bloodtsained pink slippers. The slippers have a contrast to his hoodie
with a black line at the base of the slipper that goes to the under.
separating the pink slippers! to the pink front piece (I don’t know how to
describe slippers well), at the back of the slipper are two lines, the upper
line being pink and the lower line being pinker.

Personality

(#1) Killer!Sans is very thoughtful but not to the point of feelings
usually, enjoys killing most of the time, hates being belittled, and
generally is a negative character. Killer also seems to suffer from
multiple personality disorders, as at times (with whatever magic is
left) a tiny speck of an eye will appear in his right socket, this is
classic Sans trying to get out. This is when he'll have little
breakdowns and freak out a little, as he's beginning to feel again and
he's reminded of the pain he's caused, not only that but he also has a
shadow-like Papyrus that will sometimes appear to him. This is his guilt
going into overdrive as his sins crawl up his spine...
(#3) tho during his snap mode (most of the time) is blank, and veary

(#2) a tiny speck of an eye will appear in his right socket, this is
classic Sans trying to get out. This is when he'll have little
breakdowns and freak out a little, as he's beginning to feel again and
he's reminded of the pain he's caused, not only that but he also has a
shadow-like Papyrus that will sometimes appear to him. This is his guilt
going into overdrive as his sins crawl up his spine...

Abilities

Real Knife: Causes 99 damage



Sharp Bones: Usually has high attack but deadly when attacked at the sharp point.


Way More HP: Because of him having determination like
Chara, he has gained way more health points than most other Sans, though
it's unknown how much exactly.


Reset: He has the power to reset the timeline, but if he
does this his stats will be reset, making him LV 1 again but still with
his memories, though he can save which makes up for his reset.


Note: Killer!Sans has no Gaster Blasters except for one giant
goop-spilling Gaster Blaster. Although its full power is unknown, he
usually uses it either when he's bored of his opponent or wants to end
the fight very quickly.

Relationships

Nightmare!Sans

Killer!Sans loves to mess around with him. He is one of the only
people who Nightmare talks with normally. He's the leader of the
Nightmare Team in which Killer!Sans is included and is a valuable
member. Nightmare keeps check of Killer that he remains in his dark
state by reverting his soul back to its emotionless state from time to
time, even though Nightmare has a big rival when it comes to the soul of
Killer.

Chara (depending)

Chara was Killer's Genocide partner, purely hated rival, had a bad time somewhere, or hated enemy. It depends on the user.

Color Sans (friend)

Killer has somehow become good pals with Color, and they seem to get
along quite well. Color Sans consistently attempts to revert Killer back
to his "feeling" state (which is almost always foiled by Nightmare).



Sharp Bones: Usually has high attack but deadly when attacked at the sharp point.


Way More HP: Because of him having determination like
Chara, he has gained way more health points than most other Sans, though
it's unknown how much exactly.


Reset: He has the power to reset the timeline, but if he
does this his stats will be reset, making him LV 1 again but still with
his memories, though he can save which makes up for his reset.


Note: Killer!Sans has no Gaster Blasters except for one giant
goop-spilling Gaster Blaster. Although its full power is unknown, he
usually uses it either when he's bored of his opponent or wants to end
the fight very quickly.