I can't delete endpoint, that was created by me previously

It sounds like you're dealing with a requester-managed VPC endpoint, which is created and managed by AWS services on your behalf. These endpoints cannot be deleted directly by users. To resolve this issue, you need to identify and delete the underlying AWS resource that created this endpoint.

Common AWS services that create requester-managed endpoints include RDS Proxy, ElastiCache Serverless, and other AWS PrivateLink-enabled services. Here are some steps you can take to resolve this:

1. Review your AWS resources to identify which service might be using this VPC endpoint. Look for services like RDS Proxy, ElastiCache Serverless, or other PrivateLink-enabled services in your account.

2. Once you've identified the associated service, delete that resource. For example, if it's an RDS Proxy, delete the proxy.

3. After deleting the associated resource, wait for a few minutes. AWS should automatically clean up the requester-managed VPC endpoint and its associated network interfaces.

4. If you're still unable to delete the VPC or the endpoint after this, check for other AWS services that might be using the VPC or creating requester-managed resources.

5. You can also try searching through your CloudTrail logs (if the endpoint was created within the last 90 days) to find which service created the endpoint.

If you're still unable to identify the service or delete the endpoint after these steps, you may need to contact AWS Support for account-specific guidance. They can help identify any hidden dependencies in your setup.

Remember, the key to resolving this issue is to focus on removing the underlying service or resource that created the endpoint, rather than trying to delete the endpoint directly.
Sources
I cannot delete a VPC Endpoint | AWS re:Post
Cannot disassociate or delete an elastic IP address, and cannot delete VPC endpoint | AWS re:Post
Can not delete VPC. Endpoint does not exist. | AWS re:Post