[Levin]

Last one I watched was Signal.
Saw entire series in 2 days

It was engaging in beginning but ending was so bad I decide never to watch another k drama...

The Zombie move Alive! Is very good.

Yeah, Signal is really good.

For the detective/crime genre, you can try these:

• Missing Noir M (2015). Do note that Missing Noir M has an open ending just like Signal. But it does not impact the earlier cases. Some cases take 2 episodes to resolve. Some take 1 episode to resolve.
  
• Stranger Season 1 (2017)
  
• Tunnel (2017)
  
• Children of Nobody (2018)
  
• God's Gift - 14 Days (2014)
  
• Partners for Justice Season 2 (2019). Need to watch season 1 which is quite good.
  
• Designated Survivor: 60 Days (2019). Considered political genre and I preferred this over the US original.
  
• Kairos (2020)
  
• Punch (2014)
  
• Law School (2021)
  
• Ghost (2012)
  

There are two others which I really like just until the ending. They are a bit like Signal. Great just until the end.

• Life on Mars (2018) - Remake of UK series. There's a US remake too. Great till just the end. The ending not that good just like Signal.
  
• Nine: Nine Times Time Travel (2013)
  

If you prefer a more recent series (besides Kairos and Law School which are listed in the first list). You can try these (in order of my preference):

• Monster
  
• Mouse
  
• Flower of Evil
  

If you want to venture outside the detective/crime genre, you can try these:

• My Mister (2018)
  
• Mother (2018) - Remake of Japanese series.
  
• Misaeng: Incomplete Life (2014). I prefer the Chinese remake.
  
• Live (2018). Can be considered Detective/Crime genre but more a slice of life series of a few cops.
  
• Go Back Couple (2017)
  
• What's Wrong with Secretary Kim (2018)
  

They are are others but I think enough for now.