I'll be salty if Dowun was the endgame, he's no evil, he's just a coward, his talk and his act are contradictive, he didn't want to admit he needs Lyon as well and now he felt threatened and win in the end just because of the catalyst (aka Baek Han) and ML tag? bullshit, he needs to get lectured and reap what he did like Onodera in Nisekoi.
He can win, he will win 100% in the past if he act nice to her a bit, now that Lyon loved another man, i'd support her with Baek which clearly made her comfortable like Chitoge to Raku. The classic quote if you loved 2 person, choose the second because if you love the first you won't even love the second. The girl is tired, she deserves better.