G Dragon is probably K-Pop's most prolific and successful writer. He has many more songs with one more non-idol writer credited, such as Teddy. Most of Bigbang's title tracks were written only by members of Bigbang. Most of GD's solo songs were written only by him.
G Dragon
If You
Shake It
Who You
Lies
Put Your Hands up
This Love
Ma Girl
Victory
Middle Fingers Up
Bullshit
Shake The World
MichiGo
Fool
But I Love You
I Don't Understand
Bigbang
Crazy Dog
Without You
Today
Coup d'Etat
Strong Baby
Foolish Love
Last Farewell
Obsession
What Do You Want
Bringing You Love
Love Club
A Boy
Heartbreaker
Breathe
Butterfly
Gossip Man
Korean Dream
She's Gone
Don't Leave
I Love It
G Dragon & TOP
Flower Road
We Belong Together
Forever With You
Wonderful
Hands Up
Somebody to Love
What is Right
Cafe
Stupid Liar
Fantastic Baby
Ain't No Fun
Ego
Feeling
Bingle Bingle
Baby Goodnight
Knock Out
G Dragon, Daesung
Wings
G Dragon, TOP, Taeyang
Goodbye Baby
Last Dance
G Dragon, TOP, Taeyang, Daesung, Seungri
La-La-La
VIP
We Are Bigbang
B.I and Bobby of iKon. As with GD and TOP, occasionally there's another non-idol writer but rarely more than one. These are just their iKon credits, they have other solo song credits too.
B.I
Killing Me
Just For You
Perfect
Holding On
B.I & Bobby
Just Another Boy
Wait For Me
Welcome Back
Rhythm Ta
Today
Airplane
Dumb & Dumber
What's Wrong
Anthem
B-Day
Jerk
Hug Me
Sinosijak
Just Go
Freedom
Only You
Cocktail
Goodbye Road
Don't Let Me Know
Adore You
Ah Yeah