small and angry but mostly small

Xie Lian's cultivation path is religious; he's a devote daoist and meditation and following its tenants bring him power.

Hua Cheng's cultivation path is just as religious, but his religion is literally Xie Lian. That's where he gets his power. There is a trope in Wuxia & related genres (these are gods so not technically Wuxia I think but I don't remember the specific name) where someone cultivates and meditates as a hermit in a cave until becoming a master. The Cave of Ten Thousand Gods, the Kiln... Hua Cheng did that, and we can tell what he was doing in there was worshiping Xie Lian.

And with that... He literally gets power from Xie Lian in a more obvious sense. He & his spiritual weapons get stronger when kissed and complimented, since they're being blessed by his god. The butterflies swarming when XL tells them good job. E'ming being able to grow to normal size after having shrunken due to XL praising him and giving him a kiss (which people keep acting like is a blowjob metaphor as if that wouldn't imply HC is a grower and not a shower which I think would be dumb), HC himself being able to heal and start getting bigger when XL gives him a kiss, too.