Earlier...
Tyler had killed Citrus with an attack capable of destroying even her soul despite his earlier intentions. This was purely unintentional; he had simply overestimated his opponent's capabilities.
Despite the negative emotions he had instilled in her due to the negative(despair) energy his body constantly emitted as a necromancer. The only reason he also wasn't affected again was due to the Death Shadow Ring on his person.
The Divine Tier artifact not only granted him immunity to negative energy but also boosted his efficiency with using negative energy was also increased by 20%.
Still, he hadn't expected her to die so easily. Especially after noticing how she had somehow discarded her fears, suddenly losing any trace of hesitation when facing an enemy she couldn't predict.