Odyssey Monsters:

Scylla/Skylla-> The Shredder, The One Who Tears Apart, The Mangler Coming most likely from the ancient verb σκύλλω which means "to tear to shreds" or "to rend" or "to mangle" (This verb probably gave the modern day name to the "dog" σκύλος from the fact that the canine's teeth and jaws tear apart flesh and also the modern day σκύλα means "female dog" or more fittingly "bitch" as an insult too the same way as in english. I suppose it also helps that Scylla was said to make puppy sounds to lure her prey)

Charybdis-> The One who is Agape and Spits Out Although the meaning is not 100% certain it seems to come from the verbs χαίω "to be agape", "to be open" and βδέω "to throw up" , "to belch"

Sirens -> The Searing Hot Ones, The Blinding Bright Ones From the word σειρός which means "scortching hot" and "bright" (As per my other analysis you can see here Sirens represent the dangerous knowledge that consumes and kills you if you accquire it)

Cyclops -> Round-Eyed From the Greek κύκλος "circle" and ὄψ "eye" As per the name Πολύφημος Polyphemus his name means "The One Much Sung About" or "The One with Much Fame" from Greek πολύς "much" or "many" and φῆμις "speech", "talk" "fame"

Laestrygonians -> The Skin Harvesters Once again not totally clear definition but could be coming from the words λαισήϊον "raw skin with hairs still on" and the verb τρυγάω-ῶ "to gather" or better "to harvest"

Suitors:

So I would assume the Homeric suitors because I totally am not to go through all the list of the hundreds of names suggested by Apollodorous hahahahaha So apart from Antinous, Eurymachus and Amphinomus, Homer names 12 names more (I have made another answer you can see here)

Leiodes -> Smooth-Like, Even-Like Coming probably from the adjective λεῖος which means "smooth" or "even" while the epithema -δης on occasion means "resembling"

Eurydamas -> The Tamer of Many From the word εὐρύς which means "wide" or "plenty" and probably the verb δαμάζω which stands for "to tame" or at times "to break" (in the essence of taming)

Le(i)ocritus -> The One Of The Smooth Decision, Smoothly Judged, Even Judge, Smoothly Chosen, Evenly Judged Possibly from the word λεῖος aka "smooth" or "even" and the verb κρίνω aka "to judge", "to decide" and therefore the word κριτός "the one judged" or "the one chosen"

Agelaus -> The Leader of People From the verb ἄγω "to lead" and λαός "people"

Amphimedon -> The One of Two Thoughts, Double-Thinker I had to take a wild guess for this one since the meaning is not perfectly clear. I would estimate comes from the word αμφί "both of two things" or "two things" or "two sides" and the verb μένδομαι "to think" or "to be mindful"

Elatus -> Metal One, Armored One, Fir Tree Possibly coming from ἐλατός aka "made out of metal" Same word is used in modern Greek to speak on the fir tree

Eurynomus -> Of Wide Share, Much Distributing Probably emanating from εὐρύς which means "wide" or "plenty" and νέμω aka "to share" or "to distribute"

Euryades -> Widedly Sung, Much Praised Once again I had to take a very wild guess because the second part could derive from words that mean "pleasant" or "hated" haha but I think this fits better. coming from εὐρύς "wide" or "plenty" and ᾁδω "to sing" or "to chant" if it comes from the word ἡδύς aka "pleasant" then his name could be "The One of Many Pleasures" or "Much Pleased"

Demoptolemous -> Warrior Of The People From the ancient word δήμος aka "people" (in the political essence aka a mass of citizens of a place) and the word πτόλεμος which is an alternative of πόλεμος aka "war"

Peisander -> The Persuader Of Men From Greek πεῖσις "persuasion" or "obedience" (coming from the verb πείθω "to persuade") and άνδρας "man"

Polybus -> The One With Many Oxen Most likely from the word πολύς "many" or "much" or "plenty" βοῦς "ox"

Ctesippus -> The One Who Possesses Horses, The One Who Acquired Horses From Greek κτάομαι-ῶ μαι "to acquire" or "to possess" and ἵππος "horse"

Now for the two names

Pandarus -> Of All Pelts From Greek πας aka "everyone" or "all" and probably δέρας "fleece" or "pelt"

Cebriones -> The One From Cebrenia Probably indicating his city or area of origin, named after the river god Cebren (Κεβρήν)

I am not sure what other "underrated warriors" I can include here so if you have something specific in mind I can see what I can do. For example I remember Hyppothous -> "Fast Horse" or "The One With Fast Horses" from the word Ἱππος "horse" and θοος "fast"