Sunteleo (συντελέω) means to bring fully to completion, to finish, or to fulfill entirely. The compound syn (together, fully) + teleo (to complete/achieve) adds intensity: not just ending but bringing everything to its full purpose. It appears in Jesus' temptation (Luke 4:2 — when the forty days were 'ended'), in the new covenant prophecy (Hebrews 8:8, quoting Jeremiah), and in Mark's summary of Jesus' teaching.
Sunteleo in Hebrews 8:8 is pivotal: 'The days are coming, declares the Lord, when I will make a new covenant' — the same passage Jeremiah promised. The new covenant is God's great sunteleo — the full completion and fulfillment of what the old covenant anticipated. When Jesus says 'It is finished' (John 19:30, tetelestai), it shares the same root — the full completion of the Father's redemptive purpose.
The temptation of Jesus 'ended' (sunteleo, Luke 4:13) — and so did the temptation of the first Adam in Eden. But the outcomes were opposite: Adam yielded; Jesus prevailed. The full completion of evil's assault on the second Adam came to an end, and Jesus emerged victorious. Every temptation has a sunteleo — an ending. Paul reminds us: 'No temptation has overtaken you except what is common to mankind' (1 Corinthians 10:13).