I have been recently watching ugly alert and in the drama the main couple is always opposed by a lawyer who wants the girl for himself. Please recommend me a drama where the main couple, becomes a couple either midway or at the beginning of the drama, but there is a guy/girl who wants to break them up cause they like one of them.

The Princess' Man | period drama with emphasis on romance. They do get together almost at the beginning, but there's several people trying to keep them apart (including the second male lead). 

Suspicious Partner | the leads get together about halfway through the story. There's a girl (ML's ex) that tried to get in between them but it doesn't last. 

Kill me, Heal me | ML has 8 personalities. Though the leads get together halfway, two characters are opposed to the couple (one of them is one of ML's personalities). 

While you where sleeping | they get together about halfway there. 2ML likes the FL but he doesn't really try to keep them apart, though there is a character who opposes the relationship. 

In From 5 to 9 the main couple is together from pretty much the beginning, but there are obstacles for sure. Same in Date, sorta.

Fantastic

Nice Witch

Marriage, Not Dating

and

Mask

all have couples that get together early on or in the middle. They don't necessarily have someone trying to break them up, though? Or at least that's not their main issue...

✔️ My Secret Romance 

✔️ Robber 

✔️ Murphy's Law of Romance

✔️ What's Wrong with Secretary Kim 

✔️ Wok of Love 

✔️ Secret Garden (his evil mom and his ex)

✔️ Just You 

✔️ Falll in Love with Me 

✔️ Shopping King Louie 

✔️ My Beautiful Gong Shim