Remove any resources you created within each Combine VPC.
Goto the Amazon S3 console and empty the combine-<shard id>-app-storage-<account number> and combine-<shard id>-app-storage-<account number>-public buckets.
These buckets can be deleted if they only contain basic shard information
Click the checkbox next to the target rule group and click "Delete" in the upper right.
Goto the CloudFormation console and delete each Combine VPC CloudFormation stack. (These are typically named Combine-VPC-<Id> but are also identified by a CombineId Output Value of combine-vpc.)
Goto the EC2 Key Pairs console and delete any Combine EC2 Keys.
If shard id was not set these are named Combine and CombineRestricted.
If shard id was set these are named Combine<ShardId> and Combine<ShardId>Restricted.
Delete any Combine ACM Certificates (if you are on 3.13.1 or before).
Delete the Combine Policy CloudFormation stack. (This is typically named Combine-Policy but are also identified by a CombineId Output Value of combine-policy.)
Delete the Combine CloudFormation stack. (This is typically named Combine. In 3.13.2.1 and later this is also identified by a CombineId Output Value of combine.)