My pleasure!
These are things the court may think warrant either a termination of parental rights, or a termination of custodial/visitation rights (these are NOT the same thing!) :
Parent moving in/marrying/living with/hooking up with with a convicted child sex offender
Parent abusing and/or neglecting the child - with PROOF.
Parent cooking & selling meth from the child's home
Parent being convicted of killing/seriously injuring/abusing another of his/her
own children
Parent being responsible for the other parent's non-accidental death (although this is not a given, perhaps surprisingly)
Parent becoming physically or mentally incapable to care for the child (think coma and institutionalization, not amputation of a limb and bipolar on medication - and don't assume that the presence of PTSD with TBI is automatically considered dangerous ... because it's NOT).
These are things the court may think warrant heavily restricted and/or supervised visitation rights at least in the short term
Absolutely no prior contact with the child - although if the parent runs with the child or otherwise "hides" the child, that parent needs to be prepared for their own custody to be challenged ... perhaps successfully.
Drug use which is directly affecting the child's welfare (and no, that's not a given either)
Domestic Violence conviction/s (against the parent - not an ex, as a rule)
Living with relatives who may have serious criminal histories which may place the child at risk
These are things the court typically won't see as a threat without there being a significant history of the same stuff already present
One parent being a complete jerk to the other
The parent who is, for all intents and purposes, a functional alcoholic or pot-head
The parent having an "overzealous" new partner/spouse/treat-of-the-day
Parenting differences including disciplinary measures, food choices, movie choices, PC use
Obviously these are not all-inclusive (or, indeed, all-exclusive) but they may provide the unaware some awares to think about.