Restless Webtoon
Although not really a fan of omegaverse, as it usually pictures rape and non-consensual relationships, I really liked how this author portrayed the Alpha and the Omega in this story. Their relationship evolves through time and becomes one with true feelings. There's no usual talk about "not being able to hold back" while having sex (between the main couple; there are flashbacks of rape and non-con sex from the past). Also, the art is really giving it to me. The characters are very proportionally drawn and facial expressions they make are really one of, if not 'the' best ones I've seen in a webtoon so far. Although short, very sweet indeed!
Hatsukoi Wa Gunjou Ni Tokeru
The characters' relationship move in slow and healthy way and the whole thing is portrayed pretty realistic, too. It wasn't too short or too long, but sweet. Not the best manga I've read, but still enjoyable.
Dark Heaven
Yours to Claim
Don't Touch Me! (Zhuang ning)