Create a new key-pair in the AWS console and boot up a new instance (assuming the attacker is removed from IAM users). This requires configuring the instance, which can be time-consuming ...

6. Choose Key Pairs from the Network and Security tab drop-down, and then click the big orange button at the top right that says Create Key Pair. For Key Pair settings, apply the following: Name: ...

Nick Hardiman shows you how to set up a secure connection to an Amazon EC2 machine using PuTTY and Pageant to handle your private key.