postremo quid aliud isti faciunt, cum te soli ex Sicilia laudant, nisi testimonio nobis sunt omnia te sibi esse largitum quae tu de3 re publica nostra detraxeris?
Finally, here what other thing do they make - when they-only-people from Sicily praised you - except there are all things for us as testimony that you gave them (many things) that you have took from our Republic?
“te sibi esse largitum” => obviously acc + infinitive, but I wonder if we can take “largitus” here or not, cause Verres is a man and it seems more approriate by using “largitus”
omnia is the object of esse largitum, and the antecedent of quae. The subject of testimonio nobis sunt is the same as the subject of faciunt, i.e. Verres’ Sicilian supporters.
quid aliud … nisi is “what else … except”
“What else do they do, when they alone from Sicily praise you (i.e. when they’re the only ones from Sicily to praise you), except being proof to us (lit. unless they are for evidence to us) that you gave them everything that you took from our republic (everything that you deprived our republic of)"?
i.e. All they do is prove that you bribed them. (esse largitum is more than just “gave”, more like lavished generous gifts, often used of bribes.) He’s saying they’re corrupt, corrupted by the corrupt Verres.