Some of the songs below are my favorite underrated songs!
Shadow Play - Pink Fantasy
Flamingo - Botopass
Drum - Checkmate
Obliviate - Lovelyz
Red Sun - Dreamcatcher
Think of Dawn - GHOST9
Girls - Nature
Who Dis? by Secret Number
Red - The Rose
Now or Never by APRIL
Precious - ATEEZ
Queen by 3YE
Oh Ya Ya Ya - Lunarsolar
Kitty Run by AleXa
Promise - ATEEZ
Firework - Twice
Can't get you our of my mind - Dreamcatcher
Sphinx - THE9 (Cpop)
Dead or Alive - Oneus
I'll Try - Day6
So Cool - Day6
MTBD - CL
Thnx - CL
I Quit - CL
You and I - Park Bom
4:44 - Park Bom feat. Wheein
Lovely - Minzy
Kiss - Dara
Missing You - 2NE1
If I Were You - 2NE1
Ugly - 2NE1
Gotta Be You - 2NE1
Icarus - JJP
The Day - Jinyoung (JJP)
Touch - Jus2
Runaway - GOT7
끝 (The End) - GOT7
Enough - GOT7
Any of GOT7's Japanese discography (Superman, Love Loop)
Ringa Linga - Taeyang
FXXK IT - BIGBANG
Loser - BIGBANG
The Last Farewell - BIGBANG
Lies - BIGBANG
Haru Haru - BIGBANG
Here are my recommendations off the top of my head:
Sixteen ~ Samuel
One ~ Samuel
Butterfly ~ WSJN
Boom ~ NCT Dream
That's a No No ~ ITZY
Ting Ting Ting ~ ITZY
You Smile ~ Astro
Baby ~ Astro
Dope ~ BTS
A ~ Got7
Rhythm Ta ~ iKON
Anthem ~ iKON
Beautiful ~ iKON
Be Mine ~ Infinite
AIR ~ Infinite
Bad ~ Infinite
Bounce ~ JJ Project
Mamacita ~ Super Junior
Lo Siento ~ Super Junior
Jungle ~ Super Junior D&E
Sweater & Jeans ~ Super Junior D&E
Sugar Free ~ T-ARA
Mama Mia ~ KARA
Also, I don't know if you are into mashups or not, but the youtube channel Miggy Smallz has all of my favorites . I hope you find some new bops!