In his Loeb Classical Library translation of Ovid, Metamorphoses
13.45, Frank Justus Miller translated "hortator scelerum" as "criminal." In his revision of Miller's translation, G.P. Goold made no change to that rendering. Ajax is speaking, trying to convince the Greeks that he (and not Ulysses, the hortator scelerum) should be awarded the arms of Achilles. The phrase is borrowed from Vergil, Aeneid
6.529, where it also refers to Ulysses: see Neil Hopkinson's commentary on Ovid, Metamorphoses, Book XIII
(Cambridge: Cambridge University Press, 2000), p. 88. Horace Gregory seems to translate the phrase as "bland liar," and Rolfe Humphries' translation is so loose that no trace of the phrase can be found. Translate "counsellor of crimes" or "encourager of crimes."
Id., lines 341-345:
Why does Ulysses dare to go out beyond the sentinels, commit himself to the darkness and, through the midst of cruel swords, enter not alone the walls of Troy but even the citadel's top, steal the goddess from her shrine and bear her captured image through the enemy?
cur audet Ulixes
ire per excubias et se committere nocti
perque feros enses non tantum moenia Troum,
verum etiam summas arces intrare suaque
eripere aede deam raptamque adferre per hostes?
"Not alone" for "non tantum" in line 343? It's possible (Oxford English Dictionary
, s.v. alone, sense B.1), but I'd translate "not only" or "not just."