Highest probability of winning that you have had?

80%

Edit: I had my number wrong, And I still lost, btw.

100%. This is the giveaway.
Edit: Just realized that it's a group giveaway so it's unlikely you'll see it. It's just a giveaway that only I participated.

There are a lot of 50% chances in groups, often times even 100%.
Not to mention those 1000 key giveaways where entries are below the amount set. (Would that mean higher than 100% chance?:D)

Around 19000 users will answer 100% with this public giveaway

26% on private last month, 100% once only that the private when i only entered with creator request to create the GA.
On public i think 4-5% if i remembered..

100% in Alpha Runner (3,000 Copies) with <2000 entries. Did not win cause got suspension before giveaway ended ¯\_(ツ)_/¯

57% - also the only win (forum GA)

50% on a private giveaway.

I'm so unlucky that I'd probably lose 100%-winning-chance entries.
*shoots himself*
*out of bullets*
*angrily kicks desk*
*breaks toe*

Naaah.
I usually opt out of giveaways for which I'm under 0.15%, e.g. 1-copy giveaways that are above 750 entries.
And depending on my global interest for the game (and whether I'm in needs of points for other giveaways), I can be even more selective.
This keeps my daily chance between 8%-15% according to the Stats page.
And reading the discussions and doing puzzles helps boost my chances (got my first and only win thanks to that!)

100% with that one - https://www.steamgifts.com/giveaway/D4ril/rescue-love-revenge
10 000 copies and 8000 entries

I've won a couple of 100% ones..

I also managed to not win a giveaway with 98% chance to win (50-copy giveaway with 51 entries) ;-)

500%
5 GAs and I was the only participant

100%

This stat is more explicit:

View attached image.

Not sure because I can't see any stat that shows it, but I did find a giveaway with 5 entries which I was part of.

5% - only entering for wishlist games...

33.33%
After two rerolls, I "won" ^^

13% lol and I still managed to won a GA and on a wishlisted game too, with a 2% probability but it was my Grandma's 95th birthday so maybe she was blowing on the dice for me.

33.33%

100% with a couple of 1 entry giveaways.

100%

100% several times, both as the only entrant to a group giveaway and in big giveaways where the number of entries was less than the number of gifts.

90%, still didn't win.