more important than anything else; supreme.
equivalent in seriousness to; virtually the same as.
less important than anything else
What is the word that completes the trio with a matching suffix?
According to the American Heritage Dictionary, the words paramount and tantamount do not share any roots:
paramount [AN paramont : OFr. par, by (< Lat. per) + OFr. amont, above.]
tantamount [< obs. tantamount, an equivalent < AN tant amunter, to amount to as much.]
So not only is there no trio to complete, you don't even have a duo.