This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Kenan & Kel
The clip show.
The end of Bye-Bye Kenan (Part 1).
Just the ending, Kel returns to the Rockmore house to see everyone is gone. After failing to reach contact with Kenan, Kel leaves behind what he originally wanted to give his friend: A giant portrait of the two together. Even if you say Kel really Took a Level in Dumbass later on, you know he loves his friend..
"Kenan to Kel". "Kel to Kenan." "I'm gonna miss you man.." "Me too.."
From the same episode: Near the beginning, Kel asks Kenan, via walkie-talkie, if the Rockmores' family meeting is over. Kenan, having just learned that the family will be moving to Montana and his parents definitely won't change their minds, hesitates and then solemnly informs Kel "Yeah... it's over..."
During Bye-Bye Kenan Part 2, one of the new neighbors brings over orange soda. Kyra says Kel loves orange soda...and then Kenan excuses himself from the room.
In one episode, Kel was kicked out of the Rockmore house for his incompetence and getting Roger injured. When at the restaurant Kel saying "I have a broken heart" was pretty sad.