Mother is great, strongly recommend it. There's also a japanese (original) series:
https://mydramalist.com/312-mother
I've not watched it, but it's also great I've been told. I plan to watch it soon.
Hi bye mama is also awesome, it's actually the 2nd or 3rd kdrama I watched and it blew me away how strongly emotional it was, a total tear jerker. So it has a special place in my heart, I think about it sometimes, even after watching 130 series after it Hi bye mama is special. I plan to rewatch it.
Smile has left your eyes / hundred million stars from the sky, is also a great series, but at times it was rather slow progressing.
Not seen the others ElBee listed, but I'm gonna watch some of them.
Also these are great:
Flower of Evil (more of a thriller but a heavy emotional drama)
... wow I thought I'd be able to add more tear jerkers, but couldn't.
Maybe this one:
Goblin (more of a fantasy than a tear jerker but very emotional story and scenes)