dunno about absolute #1 so i'll just include the ones i remember the most.
probably my worst was almost dieing when i went out to colorado because my appendix burst on the plane after it being bad for a year and a half. idk if the end was the worst part tho because while i was sick my grades plummeted during my 10th and 11th grade years, i lost several gfs because i never wanted to go anywhere and threw up all the time and didn't wanna eat like i normally do so i lost like 50 pounds, idr but i probably bearly weighed 100lbs after having it removed. so all of that+breaking up with my last gf at the time and having my grandfather die after being sick for years 6months before i had it removed left me pretty depressed the rest of high school.
and a couple months ago my childhood pet died in my arms, was the 2nd time iv ever seen my father cry, idk if it was because my dog died and everyone was so attached to him or because I was so broken up about it.
Iv had elderly relatives die the closest being my grandpa on my father's side but none of them were sudden so i spread the sadness of knowing they'd be gone and spending time with them over years and i ended up not being able to cry at any of their funerals.
my gf's 13 year old cousin died in her sleep a few months before my dog and the doctors never found out how or why her mother just walked in and found her dead in bed still looking like she was asleep. the worst part was they hadn't seen eachother in like 5 years since my gf moved from their hometown so the first time she saw her since moving was at the viewing.
a few weeks ago her childhood pet (a cat she rescued from the woods) died tho i kind of forget what she said happened, burying it for her and seeing her crying just tore my heart out tho.