This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Adventures of Sonic the Hedgehog
In Sonically Ever After, after defeating Robotnik, Sonic talks to the audience saying that "Every story must end, even this one". And mostly this is the last episode, if you don't include the Christmas episode makes what Sonic says sad.
In truth, Sonically Ever After was the penultimate episode of the series going by production code.
Robotnik's character is actually more TearJerking than you think. Sure he is evil and is hated by everyone but think about it why did he become evil in the first place? Let's see, his mom constantly abuses him and is always favored by his cousin, we really don't know what happened to his father but he probably never loved him, everyone pretty much hates him and he always creates robots as his army/servants and he probably never had any friends, so is it possible that Robotnik became evil because he's depressed and has never had anyone in his life that loved him or cared about him? The answer is up to you.
How about Sonic getting depressed and heartbroken over Tails moving in with his "real family" in "Tails New Home", coupled with a flashback which tells us how he met the orphan kid in the first place? For Dramatic Irony, this happened because Sonic wanted to find Tails a new home to protect him in the first place.
Tails having to say goodbye to Goopster in "So Long Sucker." He knows that he'll never see his beloved pet again, and he tearfully waves goodbye to him. When Sonic then offers to take him to lunch, Tails, looking slightly miffed, says no thanks, but Sonic says he'll get him another pet (although not an alien this time), making this a Heartwarming Moment.