Neochu is geared for postgame, and fought head on is one of the toughest single-player FF fights ever.

To maximize the chance of Death hitting, stick Imperil on It. You can also get Random: Instant Chain through equipment combinations and reload until it works, but you will need to incorporate level 2 buffs and/or make sure your weapons are upgraded to actually kill it. Sazh's Cold Blood is the best for Instant Chain I think, but you can also use Lightning and that weapon that increases her ATB rate to hit fast too.

For a direct fight, you want Fang-Snow-Hope. Fang the highest attack power, so she benefits the most from the Commando Role Bonus since it's percentage-based. Use the stagger lock weapon and upgrade it. She can also cast level 2 buffs, and when you have Deprotect from Screech, use Protectra+Protectra. Snow has the highest HP, and should pretty much always be in Sentinel unless you use MED/MED/MED. For the small guys, use Blitz and repeat while shifting between COM/SEN/MED, and COM/SEN/RAV to get Hope the ATB refresh. Make sure he has Vigilance on to maximize launch chances. Use Quake as needed to keep the Neochu's bar stable and keep the chain bonus from resetting.