κύντατον
This superlative adjective is found only here in the Homeric epics, but we should note that thirty manuscripts, according to Allen, have the comparative κύντερον instead, as does p425. Other uses of the comparative in the Iliad and Odyssey describe situations of suffering loss and perhaps also attempting to avenge it: it is used of Hera when she wants to defy Zeus and help the Achaeans in the war (Iliad 8.483); of Clytemnestra, who kills her husband Agamemnon and avenges her daughter’s death (Odyssey 11.427); of the insistence of a hungry belly, overriding all other concerns (Odyssey 7.216); and of the day that the Cyclops eats Odysseus’ men (Odyssey 20.18). We can also compare its uses in the Homeric Hymn to Demeter, where the year during which Demeter is withdrawn is called κύντατον (Homeric Hymn to Demeter 306) and her grief is κύντερον (Homeric Hymn to Demeter 90). With this underlying notion of loss and grief connected to possible revenge as part of the traditional resonance of the word, in this line it may possibly allude to the version of the story of Rhesos in which he fights at Troy for one day and inflicts such huge damages on the Achaeans that Diomedes and Odysseus are sent to assassinate him at night (see “Tradition and Reception” for a full discussion of the variations of his story). Considering that version, Diomedes’ actions and his thoughts about further actions could be understood as fueled by grief over the loss of his comrades and as amounting to vengeance for them. The “need” on this night for action is similarly motivated by the Achaean losses earlier that day.