doubtful vs unchallenged

doubtful

• A doubtful person or thing. 

• Experiencing or showing doubt, sceptical. 

• Subject to, or causing doubt. 

• Improbable or unlikely. 

• Unclear or unreliable. 

• Suspicious, or of dubious character. 

• Undecided or of uncertain outcome. 

unchallenged

• Lacking experience due to lack of challenges; untested. 

• Not having any challengers.