If we’re going by cry count, then it’d be either Tomoyo After or Kanon… A total of one cry each. CLANNAD’s routes never really hit a climax, Litbus was imo (as many already know) poorly written, Rewrite had no negative feels apart from rage during the end of Lucia’s route, Air was Air, and AB was rushed.
Sadness though is totally different. I think there are only three contenders - Air, Tomoyo After and planetarian.
Air is just another link in the chain… SPOILERS FOR THE ANIME, VN AND MANGA Every single ending brought to a close the story of Yukito’s journey, and passed it down to the next person, who’ll probably mess up in the same way, and the story of an angel in pain will go on forever.
Tomoyo After is all about the treasure of life. It’s about looking at what makes life “wonderful.” When do decide they just want to… give up? Or do they instead decide to just keep struggling? It’s all about hope for the future, but hope doesn’t come without sadness.
planetarian is set in a dead world. Again, there is a message of hope for the future within the story, but that isn’t expanded on in the original story. In planetarian you get a broken robot and a broken human.
Gonna give the vote to TA because favoritism, but all three have a fairly decent shot at the title of “saddest.”