Obi-Wan Kenobi does not kill Darth Maul in their first encounter. Instead, Maul cuts Obi-Wan in half and leaves him for dead on Naboo.
However, Maul survives the battle and is eventually tracked down by Obi-Wan. Their final confrontation happens on Mandalore, where Obi-Wan finally defeats Maul. Obi-Wan does kill Maul in this encounter, but it's not their first meeting.