1246 diakatelégxomai (from 1223 /diá, "thoroughly"; 2596 /katá, "contrary to, down against"; and 1651/elenxō, "convict, proving what is wrong or shameful") – properly, "prove all the way through" (literally "back-and-forth" until finished); (figuratively) demonstrating an idea (thesis) is true by completely refuting what opposes it, i.e. to fully prevail in a debate by also putting down (2596 /katá) what is wrong (or wrongly opposes the truth, used only in Ac 18:28).

1246/diakatelégxomai ("powerfully confute") is an "intensive form of elenxō, 'to convict' (dia, 'through,' kata, 'down,' both intensive). Ac 18:28, implies that 'he met the opposing arguments in turn (dia), and brought them down to the ground (kata).' It carries also the thought that he brought home moral blame to them" (Vine, Unger, White, NT, 122).