How do you get Xu Zhus level 11 weapon in Dynasty Warriors 4 Extreme Legends?

Defeat Yu Jin.

Defeat Li Dian.

Defeat Yue Jin.

Defeat Man Chong.

Defeat Dian Wei twice.

Do not allow the Farmland Damage Spread message to appear.

Do not allow the Ally Guard Team Destroyed message to appear.

Do not allow enemy Supply Troops to successfully deliver their

supplies for more than 3 times.

Achieve 80 KO Count.

For each time a "Farmland Damage Spread", "Ally

Guard Team Destroyed", or "Supply Troop Supply Successfully

Delivered" message appears, add 10 more KO Counts.

Here's a step by step sequence.

Defeat Yu Jin before defeating his Supply Troop Captain.

Defeat Dian Wei's 3 Supply Troop Captains.

Defeat Dian Wei.

Defeat Li Dian before defeating his Supply Troop Captain.

Defeat Dian Wei for the 2nd time, it's acceptable to ignore his 3 Supply Troop Captains this time.

Encounter Dian Wei for the 3rd time.

Defeat Yue Jin after he appears (approximately 4 minutes into stage at map East), before defeating his Supply Troop Captain.

Defeat Man Chong after he appears (approximately 6 minutes into stage at map Southwest), before defeating his Supply Troop Captain.

You should receive a Precious Item Report together with the weapon learned message, the Meat Bun Sack.

Defeating the enemy generals' Supply Troop Captains (after defeating the respective enemy generals) is not necessary for unlocking the weapon, but is nevertheless recommended.

It is acceptable if enemies start pillaging. It is only unacceptable when the message tells you that farmland damage has spread.

The "add 10 more KO Counts" thing is only conjecture based on my various tests. There might be a limit to how many messages could appear before the weapon is lost, but I never tested the limits. So just keep the message appearances to a minimum and hope for the best. Or just keep them from appearing altogether. Do this on Expert mode