For me would have to be several events

Recently,
1. New Avengers #40 where it was revealed at the end that Spiderwoman was replace by a Skrull.
2. Hearing the News about the conclusion of One More Day
3. Death of Captain America. (Long time fan of him since 6 six years old)
4. Batman R.I.P.
5

Past
1. Clone Saga-They Stated Peter Parker was the clone, I knew he was not, made me wanted to stop collecting Spiderman until it was retconn back.

2.Colossus joining Magneto's army in the saga "Fatal Attractions" that move just blew my mind, I was thinking "holy cow, what in the hell is he thinking?" "oh god, why Peter, Never thought it would be him, he's just such a nice guy"

3. When they tried to convince us that the Red Skrull and Captain America were related. Then it was later revealed that they were not, the Red Skrull was just cloned from Captain America.

4. West Coast Avengers disbanding. man Scarlet Witch never looked so damn fine then in the year 1992. With her new skimpy costume.

5. Reed Richards Dead.

6. Psylocke seducing Cyclops and the whole affair.

That's all.