Hi @Vimal,
Add the following statement to the permissions policy for the IAM entity that needs to delete a service-linked role:
{
    "Effect": "Allow",
    "Action": [
        "iam:DeleteServiceLinkedRole",
        "iam:GetServiceLinkedRoleDeletionStatus"
    ],
    "Resource": "arn:aws:iam::*:role/aws-service-role/ecs.amazonaws.com/AWSServiceRoleForECS*",
    "Condition": {"StringLike": {"iam:AWSServiceName": "ecs.amazonaws.com"}}
}