For ingame purposes, you don't really need flawless or even good natured stuff. :P
Honestly. I've beat the game (HGSS) with a Quiet Typhlosion, a Quiet Starmie, a Timid Scyther, an Adamant Kangaskhan (the only good natured one in the team), a Naughty Quagsire and a Relaxed Hustle Togekiss.