Opposite of endearment terms - does it exist, and/or have a name?
As opposed to -y or -ie, -o is arguably antagonistic or alienating when added as a suffix. Bucko is defined as "a person who is domineering and bullying." Friendo was memorably used by the fearsome hitman Anton Chigurh in the film No Country for Old Men. Hunter Thompson reportedly named the paradigm-breaking "gonzo journalism" after "some Boston word for weird, bizarre." The Wictionary entry contains many negative examples ("uggo, weirdo, wino, cheapo, wacko, psycho, sicko"). When applied to a person, the connotation seems to usually be negative.
On a separate note, -zilla (from Godzilla, connoting aggression and ferocity), -gernaut (from Juggernaut, connoting invincibility and unopposability), -gate (from Watergate, connoting a distasteful scandal), are some more specific suffixes that come to mind (-tacular, etc.), but these are all from existing words, distinct from typical diminutive forms.