Only drama you'll rate 7 (actually I prefer 8) or more

Plot with substance / good plot

Lead has great attitude towards life

tagged with Comedy (preferably not main theme. not use failing as the gag)

I don't know if this is what you are looking for, but I hope it helps

She Was Pretty

Fated To Love You

Because Of You

Fight For My Way

Qeen Of The Ring

  • +1 to Fight for my Way

In addition:

  • Romance is a bonus book | FL faces a lot of failure at the start of the show. Some comedy. 
  • Haechi | ML faces failure and obstacles at the start of the show. Some comedy. 
  • Age of Youth | The FLs all face different types of failure, especially one of them. Some comedy, mostly slice of life + Friendship + Drama. 
  • Devilish Joy | Due to a scandal, FL loses everything and must work her way back to fame to bring food to the table. Comedy + Romance. 
  • Suspicious Partner | both leads face failure at some point during the show. FL a bit more than ML. Crime + Romance + Comedy. 

Beautiful Gong Shim :Nam Goongmin &Minah are  cute , extremely hot ,both hilarious af .

Don't miss out on Strongest Deliveryman. It's a wonderful underdog story and the lead has nothing but a positive attitude towards life (like you mentioned).

Sexy Voice and Robo. Despite the ridiculous title, it's actually a very good drama with some pathos. One of the leads is a robot otaku and not what you'd call a regular adult.

All my recs are Japanese

1 Pound no Fukuin 
Kisarazu Cat's Eye  (definite comedy, but maybe not to everyone taste took me abit before it became one of my favorite drama series)
Kyou Kara Ore Wa!! -doesnt quite fit the loser qualification but normal kids decide they are thugs on the first day of high school, hilarity ensues.
Nobunaga Concerto 
Uchi no Otto wa Shigoto ga Dekinai  (my useless husband)
Umi no Ue no Shinryoujo