This will be a chat of "If you could" questions, so if you had something, what would you do with it, or if you had a choice over something, what would you do.
Reality stone because the ability to change reality to my will sounds interesting. I could create something out of nothing, get rid of people I like (I won't do it), transmute stuff, just change the universe, and more. It's been shown that the reality stone by itself has multiversal levels of power.
If its the MCU (not so clear on comic stones), then we could immediately rule out the Power or Mind stone, as wielding them have serious repercussions, like being disintegrated or mind controlled. Soul stone is kinda useless, so out that goes. Now we're left with Space, Time, and Reality stone. Now I'm pretty sure that the reality stone can counter other stones, but the reality change is limited I assume or else Thanos would've just used the reality stone to wipe out half of existence. Order from best to worst IMO: Reality, Time, Space, Soul, Mind, then Power. If I could wield the last 2 without getting harmed, then Soul stone for sure is the worst.
The way that you phrase the question, I suppose stopping the September 11 attacks would be my choice. However, many people have said that killing Hitler in the womb or as a baby would have been the thing to do, but then you are killing an innocent.
If you could stop one tragedy from the past, what would you stop (No natural disasters, and no global level tragedy like the world wars. You can stop something like a persons assassination, a terrorist attack, something like that.)
My comment had nothing to do with rule 2. It was saying that if I don't let my son surpass me and I never want him to. That would mean i'm a bad parent. I don't want to be a bad parent. I want to be loyal to my family.
The rule of two states that the apprentice must surpass the master. When they do they take on another apprentice and the cycle begins again forever increasing their power
It says something about star wars? Why would I believe in anything about star wars?