【Supreme】 ,  【superlative】 ,  【transcendent】 ,  【surpassing】 ,  【preeminent】 ,  【peerless】 ,  【incomparable】  can all mean highest in a scale of values.

All of these words may be interchangeable when used rhetorically or bombastically with the resulting loss in definiteness, but all are capable of discriminative use in which they carry distinctive implications and connotations.  【Supreme】 is applicable to what is not only the highest in rank, power, or quality but has no equals in that status, all others of the same class or kind being inferior in varying degrees.

【Superlative】  is applicable to whatever, by comparison with all other things of the same kind or with all other manifestations of the same quality, admits of no superior especially in commendatory qualities, for  【superlative】 may admit equals but it excludes superiors.

【Transcendent】  and  【surpassing】  are applicable to whatever goes beyond everything else of its kind or in its quality; both can connote an exceeding even of the 【superlative】 , but  【transcendent】  suggests realization of the ideal, and  【surpassing】 suggests almost inconceivable attainment.

【Preeminent】 is applicable to what goes beyond all others in achieving distinction or eminence; it implies both superlativeness and uniqueness within the limits indicated, but it seldom carries a suggestion of direct supremacy or transcendency.

【Peerless】  and  【incomparable】  both imply the absence of equals but, commonly,  【peerless】  connotes the absence of superiors and  【incomparable】  connotes the impossibility of being equaled; while both normally refer to commendatory qualities,  【incomparable】 is also freely referable to qualities that merit condemnation.