Lu Yang realized that his mindset had become somewhat ungrounded recently and forced himself to rapidly cool down and assess his combat strength.
As the strongest Golden Core Stage cultivator to advance to the Nascent Soul Stage, capable of challenging opponents above his level, he was not incapable of fighting against those in the early stages of Spirit Transformation, especially if he added his wits to the equation; he might even be able to overcome early-stage Spirit Transformers.
This meant that he possessed the combat strength of an early-stage Spirit Transformer.
Furthermore, by invoking divine possession, seeking help from Fairy Eternity, and using the Imitation Fist technique taught by his Eldest Senior Sister to summon her, he could increase his combat strength to a whole new level.
All these advantages combined, he could indeed hold his own against an Immortal.