A developer who was on my team has left the company but I found out they had been pushing up infrastructure via Terraform locally to an AWS account, and have not provided their state file.
Is there an easy way to go and delete their infrastructure, or do I just need to find their resources and delete resource by resource?
1 option is AWS Nuke as mentioned if this isn't a shared account. https://docs.aws.amazon.com/prescriptive-guidance/latest/patterns/automate-deletion-of-aws-resources-by-using-aws-nuke.html
2nd option is to look at the account Billing details in Cost Explorer & you will see all the services you're paying for in that account. Any service you know isn't needed or should be used can be removed manually.
3rd option is to look in cloud trail and search by the user creating resources to verify what needs to be deleted. More details on that type of search here: any script to know all the AWS resources created by certain IAM user
There's no easy way if you don't have the state file. This tells me your state files aren't stored in a shared space such as an S3 bucket, which I would highly recommend to avoid this issue in the future: https://developer.hashicorp.com/terraform/language/settings/backends/s3