Noun : a stadium without a rival.    From Dictionary.com. 

Adjective : rival suitors; rival businesses.    From Dictionary.com. 

Verb (used with object) : He soon rivaled the others in skill. ,The Hudson rivals any European river in beauty.    From Dictionary.com. 

As matched well, and rivalless for gallantry and force.    From Wordnik.com.  [Song and Legend from the Middle Ages] Reference

As matched well, and rivalless for gallantry and force.    From Wordnik.com.  [Mediaeval Tales] Reference

They do not, for your oyster is ever humble even when tenanted with a rivalless pearl.    From Wordnik.com.  [Tropic Days] Reference

Mrs. Eddy, with an envious and admiring eye upon the solitary and rivalless and world-shadowing majesty of St. Peter's, reveals in her.    From Wordnik.com.  [Christian Science] Reference

White, -- yes, in a high degree; and pure, totally; but not at all dazzling in the white, nor pure in an insultingly rivalless manner, as snow would be; yet pure somehow, certainly; and white, absolutely, in spite of what might be thought failure, -- imperfection -- nay, even distress and loss in it.    From Wordnik.com.  [Proserpina, Volume 1 Studies Of Wayside Flowers] Reference