I'd bring back:

Ritchie Benaud, I miss his cricket commentaries.
Jesus (assuming he existed), just to find out if what was written about him actually happened

I would prevent:
The discovery and use of sprouts

Off the top of my head...without giving it much thought...George Carlin and Robin Williams...to provide laughter for all. The Holocaust.

Lincoln and MLK. World needs them.

1. Tom Petty .....because my world became very dark last October...
2. Isaac Asimov or Robert Heinlein.....because I need new books to read!
   Or Tesla....because we need him and his ideas.....

I would prevent the destruction of Native American (North, Meso, and South America) first nations tribes and their languages and cultures....religions and mythologies.....so much has been lost and can't be reclaimed. It's heart breaking.

1. Leonardo da Vinci. A genius and a renaissance man
2. Howard Zinn. A brilliant thinker and historians.
   There are so many disasters, that it is hard to pick. The holocaust the genocides all over the world, and Trump.

John Lennon was a genius but a wife beater and an emotional abuser of his children by his own confession. Hammurabi was a vicious despot.

Anyway, I would bring back:
Talulah Bankhead
Douglas Fairbanks Jr.

And I would prevent Brexit.

Einstein - genius
My mum - taken too soon, and I'm selfish
WW1 - the progenitor of so much that followed

fck lennon self confessed woman beater and how he treated his kid nah george harrison b4 that tool and stephen hawking dunblane shooting

1. Bruce Lee, he grew to only 33 years old but was one of the wisest men to ever have lived and I think his life over another 50-70 years would have been something amazing to see.

2. Benedict Arnold, he was a brilliant military commander and supposedly he turned traitor due to the fact that the American military was losing badly and making some very poor decisions in the war and should have lost. I'd love to hear his side of the American Revolution and also hear more about the founding fathers at the same time.

3. The burning of the Library of Alexandria, although debate rages over the scale of the tragedy and even if it was one or several events, supposedly there were countless volumes of philosophical and scientific works that did not exist anywhere else and it is unknown how much of a set back that event took but most scholars agree that humanity would be much further along if not for that event.

Martin Luther King Jr, John Lennon
The witch burnings in Europe

Gilda Radner, died too young and brought us such joy. Steven Hawking, for his genius and inspiration. I'd prevent the genocide of Native Americans. Not sure if I'd be here in that case, but so be it.

Tupac and Walter Payton. I would also go back and prevent 9/11 from occurring.

I'm not sure who I would want to bring back.
The event I would prevent from happening would be the birth of 45.
I'd make sure his parents never met.

John Adams - I'd like to have him clarify some points in the constitution
George Carlin - His perspective's always appreciated.
The burning of the library at Alexander

I would bring back Ghengis Kahn and Vlad The Impalor. The world has gotten so wrapped up in how bad things are it needs to be reminded what bad really is. The natural disaster I would prevent the dinosaur extinction.