When it comes to expressing the highest level of excellence or supremacy, there are a plethora of synonyms you can use besides "supremely." These include: extremely, highly, exceptionally, transcendently, preeminently, incomparably, superiorly, paramountly, chiefly, consummately, and ultimately. Moreover, depending on the context, you can choose other suitable alternatives such as best, top-notch, foremost, premium, elite, prime, finest, leading, etc. These expressions can emphasize the degree of excellence or importance of something or someone, and create a more vivid and colorful description. By using different synonyms, you can enrich your vocabulary and convey your ideas more clearly and impressively.