Is there any way to redeem myself for a mistake I made on this site over 2 years ago?

Try to contact one of the giveaway creators and ask them to reroll and of course give them unused key for that game.

Both were large-scale giveaways from the same user who is seldom here. The chance for you to convince him to reroll is next to zero, because finding a suitable winner after all this time for a game that had at least one gigantic massive free key drop in the meantime would take him way too much effort, and getting one key deleted from the giveaway is something only the site owner could do by manually editing the database.

Just get used to never being able to enter any SGTools giveaway. There aren't that particularly many of them.

If he didn´t reroll, simply aktivate one and mark as recived. the second one mark as not recived

Can't you submit a ticket for this fairly unique problem you have (long time ago, game has changed price, etc.)?

Are there any consequences to not doing anything about it?

Looks like you deserve a break to me. Assuming it's all true.

The important question here is -- did you use both keys?

If you did use both -- well, you're kinda screwed.

If you didn't use both and can remember which you didn't use, perhaps you can submit a ticket to support so they may advise you how to proceed with things.

there's a way to delete one of your entries in those mass giveaways, but if i remember correctly only the admin can do it (not even sure if this is allowed now).
so you would need to convince the giveaway creator, support, and wait till cg does it.

You can and should contact support, even though it might take awhile to get resolved
I wish this was somewhere on the guidelines.
I come across this problem often, and i always consider if i should reroll or not.
People end up looking guilty, not because they want to, it's a harder issue than lets say "Unactivated wins"

For SG suspension is your penalty, though its not just that,Not when everyone can keep track of your unactivated and multiple wins.

Waiting on support to see my ticket and help me with this, thx for all suggestions! Have a nice day!