Cheesypoofs I've played maybe like 30 minutes of among us lol.
Interesting role though. It might be overpowered in some ways. It might make a duo goodie group pretty strong since they can shield their friend and be assured when and if they are approached by a killer they also can't be killed at least the 1 time. With a 30 second cool down and it lasting 30 seconds, essentially the friend can have permanent shield as long as the guardian is alive. If you were to attempt to kill the guardian the 2nd time, the friend will still likely be shielded and/or just report the body immediately. This will assure the goodies will have an extremely high chance of winning. This leaves the killers ONLY way of killing them both by either dropping the floor in space crisis, or doing a face off or invisible kill on the guardian, or just simply taking one for the team and reveal their role by killing the guardian in front of the guardians partner.
In the event they're not grouping up, there's been a few times where someone is assumed to be a goodie because they could've killed someone but they didn't. Being unaware if your 1 time death prevention shield is up, a killer who attempted could be assumed a goodie by them since they don't know they were attempting a kill on them. A lot more of a minor thing, I'd say the grouping up will be a huge issue for the guardian role.