https://screenrant.com/tv-episodes-beginning-of-end-decline-show-downfall/

From Fonzie jumping the shark in Happy Days to Negan killing Glenn in The Walking Dead, some TV episodes show when the series started going downhill.

10 Infamous "Jump The Shark" Moments That Ruined TV Shows (https://screenrant.com/tv-show-jump-shark-moments/)

The term "jump the shark" is thrown around quite often, but some famously terrible twists and painful scenes really did ruin their shows.