What did you do, Hamlet?
What could accuse yourself of?
What could be so bad that it would have been better not to have been born?
The only things we see, thus far in the play are – being kind of mean to your (ex)-girlfriend, a little jerky to your girlfriend’s dad and a little jerky to your friends. All of which are totally understandable under the circumstances.
When you answer this (implied) question in the next sentence – all these “sins” are sins of thought – of pride, revenge, ambition.
But of course, these words may not be for Ophelia.
And this is a standard weapon in the arsenal of breaking up: the I’m-not-good-enough-for-you Gun, the I’m-an-awful-person-I-don’t-deserve-nice-things Slingshot.
There probably aren’t any really big skeletons in Hamlet’s closet. We probably see him kill his first person in the play. Probably.