They say Lu Bu, who fled to Xiapi after attacking Xuzhou, is unbeatable.

I just set out from Cao Cao's base, dealt with Gao Shun and Zhang Liao, and then Xiahou Dun lost an eye. Now I'm on my way to attack Lu Bu in Xuzhou. But Lu Bu, the mid-boss, is still at a high level. How much stronger will Lu Bu in Xiapi Castle be? It feels like there's no more combat power increase no matter how much I gather, and even if I get tactics books by luck or upgrade my gear to steel, it's tough. It seems like I need better generals now.