"unpredictable character" is correct and usable in written English.
You could use this phrase when describing characters in literature, television, or film. For example, "The movie had an unpredictable character who often kept the audience on the edge of their seats".
By many accounts, there has been a seemingly erratic, unpredictable character to Mr. Wahid's conduct.
It would be a mistake to think of him as an impossible, unpredictable character.
Otis Chandler, on the other hand, is a colorful, unpredictable character.
Martin O'Neill believes Roy Keane's unpredictable character will be a huge asset in his new role with Republic of Ireland.
On June 23rd IKEA said it was suspending its investment in Russia because of the "unpredictable character of administrative procedures", a euphemism for graft.
And yet its messy, unpredictable character is what makes São Paulo so intoxicating: this is a city where spaces fold into one another and lives collide.
All three actors create vivid, slightly unpredictable characters, with the astute directorial guidance of Loretta Greco.
Mancini has managed some of the most volatile, unpredictable characters in the sport, and taken them to this title.
He's drawn to "weirdos and crazies and prickly, unpredictable characters like Raymond" — characters who move him and scare him at the same time.
Mina makes a great deal of the racial prejudices that poison community police work, but her grimly funny plot really turns on the eccentricities of her unpredictable characters.
But because a devious mind is manipulating the genre conventions — allowing unpredictable characters rather than precision-tooled action to drive his story — the rules of the game are constantly changing.
