The 2005–06 season he signed a 2-year deal with Belgian side Standard Liège but failed to play a single match.
That same season Ionikos fell in the Second National Division of Greece, Beta Ethniki 2007-08, and he decided to leave the club.
In October 2007, he returned to Nikaia, at Ionikos, at a point where the club campaigned for a promotion in the Super League Greece.
For APOEL he played in 23 games in the championship and scored 8 goals helping the team to win the Cypriot First Division and the Super Cup of season 2008–09.
In May 2009, the player and the chairman of APOEL, Phivos Erotokritou, did not agree on signing a new contract and Onwuachi returned to Greece to Ionikos.
In August 2011, FIFA canceled his contract with the club after they failed to pay his salary for two consecutive months.