Ignitus' story about Cynder's past, if the fact an entire generation of unborn babies was just slaughtered doesn't do it, what was done to Cynder certainly would.
Also, Cynder's explanation at the beginning of The Eternal Night. She's leaving because her past is hurting her so much she can't stand staying somewhere she clearly enjoys being. It's clearly hard for her to leave but she feels she has to. Worse, it's not Cynder's fault at all. She's an innocent victim and blames herself for nearly 12 years of murder and destruction she was forced to cause, and is just a poor little kid!
The fact that dragons are implied to be going extinct. What cements this is how few dragons are seen, with only a few randoms in the background of Dawn of the Dragon outside of the main characters being seen. What cements this is the fact that Ignitus states that the eggs destroyed at the start of A New Beginning were vital to the species' survival, implying the dragons are boarding on extinction after so many years of war. Even after Malefor is finally defeated and the Dark Army is gone, it's unlikely the dragon species will ever fully recover population-wise, unless of course there were other eggs hidden.
The closing theme of The Eternal Night, not helped by the fact that beforehand you see Spyro, Cynder and Sparx getting to close one another as they are frozen in time and the mountain collapses around them.
Ignitus's death and the accompanying Obi-Wan Moment. You can see grief wrecking Spyro when it happens.
The ending of The Legend of Spyro: Dawn of the Dragon. After defeating Malefor, the world starts to crumble around Spyro and Cynder as they stand at the world's core. Before falling away, Spyro and Cynder help recombine the world, with them as the (presumable) cost. The credits start playing the absolutely heartwrenching song, "Guide You Home (I Would Die For You)". Right as the credits finished rolling, you get one simple message: "Thank you to all of the Spyro fans who have helped to support our favorite purple dragon for the last 10 years. We could not have done this without your continued encouragement.". For those who grew up with the series, the very idea of Spyro dying is a sobering one. It doesn't help that Word of God intentionally leaves Spyro and Cynder's ultimate fate up to fan speculation. It's one big punch in the gut to see the "Legend"-verse of Spyro at its end.
