The Titan saying goodbye hurts because they really did know Luz for a while. Watched her, talked to her, as she talked to him; Answering every spell Luz wanted or needed, saving her life and those of her friends countless times. He’s been here since at least The Intruder, probably sooner given he was watching, so it feels like goodbye to an old friend, and it must’ve been for Luz, given the glyphs were the Titan, unique to him, and how she’s lived with him for so long. Even knowingly spoken to him at the knee, when she asked the Titan to show her magic, and when he did, Luz happily accepted and embraced it, recognizing it as a gift, even if she didn’t yet know it was for being so kind to his son.
Luz must’ve grieved, not just the loss of her original glyphs and her brother’s dad, but also a companion she realized was with her since the beginning, the wonderful home she found in the demon realm. Someone she didn't even appreciate until it was too late. And he gave Luz one final gift, even as he was dying; The rest of his life, so Belos could not claim it as he did the glyphs and the Titan’s name and body, and most importantly to give Luz another chance at life.
When Luz fought Belos one last time, it was with Eda, King, and the Titan present, during joyous synchronization; As it was when she stared Philip down as he was stomped to death by the Titan’s son, avenging his father. The Titan was the friend that gave Luz the magic she needed to become a Good Witch, it’s as much because of him as it is Eda and the rest... The Titan was her mentor too. He may as well have been a dad to Luz as well, and there is the possible metaphor of Belos corrupting the Titan being akin to Manny dying of cancer.
