Is he a physical, magical, evasive or resistance tank? A mix? Generally, "tanky" characters have high Phys.Def and/or Mag.Def, average Phy or Mag.Atk, below-average Agility and varying degrees of Resist. It all depends on what type of "tank" you want him to be, really.

Also, as Tree said, stats aren't really [i]that[/i] important, they just look pretty, really. Just look at the stats of the other, already-approvedd characters and consider what you think is fair and appropriate. :)