

Probably not, it depends on what you did. I can (almost) guarantee it was one of two situations though:
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it wasn’t actually that bad.
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If it was bad enough that you did manage to actually grievously harm or even kill someone, you were almost definitely put in a situation / given access to something no sane adult should or would have ever allowed a 6 year old child to have access to (such as a gun, or being in a position to knock someone off a cliff). It is the responsibility of adults to make sure that 6 year old children are unable to harm other people while they are still learning that their actions have consequences.
As for your current everyday life, I need you to understand that an inferiority / guilt complex is in itself a burden on everyone around you. I once dated a guy with a similar guilt complex and he was impossible to deal with because I kept having to constantly shore up his self esteem for him.
If you really want to do something that benefits other people, start by working on yourself and your self esteem. You may be able to try self-help books, videos, personal mantras, etc, but if you’re not making any headway with those you likely need professional therapy. You are no good to anyone (and even a bit of a drag), if you continue on with this mindset.
Oh, and it’s also the responsibility of adults to raise children who don’t think or act like this. If the people who raised you have even subtly hinted to you that this is your fault in some way, they’re only doing it to avoid having to take responsibility for failing to prevent a six-year old child from causing irreparable harm to something. That means they failed twice, and they did both as adults.
You’re still stuck fixing it though, not because you deserve it but just by way of it not being possible for anyone else to.
Edit: I’m in a bit of a mood about my own parents right now, so if anybody else wants me to roast their parents lmk it’ll probably be very cathartic.
A marriage is a mutual responsibility of the people in it and no one else. Only those two people are even capable of upholding the promises they made to each other. If one or both of them failed to do so that is on them. And again, if they failed to help you understand that it is not your fault, that means that in addition to not being able to keep their own damn promises, they also failed to raise you properly.