Honestly, the only person (or Pokémon, in this case) that comes to mind is <Adiunna the Volcarona> - Molesurya's mother and Elio's first surrogate mother.

Despite him being young at the time (thus blameless from the external perspective), Elio berates himself for not properly noticing his foster mother's illness - especially since it was in its terminal stages; it doesn't help that she was quite skilled at feigning her wellness to prevent her children from worrying. If he was aware much sooner, he would've swiftly made arrangements for her to be properly cared for at his family's hospital or one of the various Argentium-affiliated underground facilities scattered throughout New Tork City - which are all well-equipped with the latest and most advanced medical technology (at the time), and headed by incredibly-versed professionals capable of curing even the most terminally-ill patients. This lack of attentiveness, paired with his then emotionally-stunted phase, caused him to experience the death of a loved one for the first time and urged him to hone his observation skills to their utmost; in est, it's a major root of why he's currently known as an abnormally perceptive person by most.