Ridiculous (absurd, ludicrous, preposterous)
Not in any sense ridiculous, not to the point nor fun:
Mablung (the Hunter)
Entmoot (saying it was ridiculous only betrays the suggester being ridiculous.
)
Ban of the Valar
Farmer Maggot
Oath of Feanor
Húrin
Which leaves only candidates which are neither brilliant or great either...
Grima Wormtongue - sad character rather, or then despicable, or even evil if one wants to look at him that way. But not so much ridiculous unless you wish to maintain that all puppets are ridiculous by definition.
Uruk-hai - To call the Uruks ridiculous sounds a bit odd as well. You could say deformed, twisted, cruel, maniacal, stupid; maybe mocking the nature and then by some way the products of a "ridiculous attempt at twisting nature" or something.
Saeros - I think comes the closest of the three: comparing men to animals sure is ridiculous, especially if done from jealousy (which is kind of self-contradicting) - then again, trying to ambush Túrin and get better of him far outreaches plain ridiculousness (okay, might go as ludicrous or preposterous) - and his fate is far from anything fun or to be smirked about.