Many dogs die throughout the story; the majority die of natural causes, but Sparky (Santiago's dog) and Prince (Ruth's dog) die from their fathers. Randy shoots Sparky, and Gregory leaves the house's gate open while stoned, causing Prince to walk out onto the street in search of Ruth and wind up getting hit by a car.
There are a few scenes in which a character is raped onscreen; for example, many of Erik's victims are assaulted "onscreen" in literature pieces but never in art pieces. If there is a drawn scene in which a character is being assaulted, there is no full, in-your-face shot of the assault; only cuts of the character's scenery, eyes, thought process, etc.
Sexual assault plays a huge part in serendipity, as it is essentially a coping mechanism for both creators. There are many scenes in which a character is assaulted. However, the level of severity shown varies depending on the media type. If it is in comic or drawing form, it will never be anything more than cryptically implied; however, when it is literature, it will most likely be more graphic, still keeping the cryptic or metaphoric portrayal but being more in your face.
This question is iffy. by the creator? no. by characters within the series? yes, definitely. It is very upsetting and should not be glamourized at all.
Many characters in Serendipity are victims of child abuse, especially within the first generation. Sometimes it is implied, and other times it is blatantly shown and presented to the audience. This applies to all media types.
Yes, very briefly. Queenie (Nik's cat) is abused and ultimately killed by her manager, and Luda (Scorpion's dog) was briefly abused by the Kozarians until he and Wolfgang were taken in by the García-Fernández family.