Callous

[Jessica]

emotionally hardened; cold-blooded and indurate to public opinion;

[Mark Zuckerberg]

Not giving a rats ass about anything.
The extreme of all [apathy].
Not giving a fuck.
Lack of all things binding ones emotions to any actions they commit.

[Becky]

[Uncaring], [indifferent] or unconcerned about the feelings or needs of others, [heartless], [cruel].

[Sonia]

thick-skinned english teacher

[Rihanna]

[Uncaring], [indifferent] or unconcerned about the feelings or needs of others, [heartless], [cruel].

[Sarah]

Hardened in mind; insensible; unfeeling; unsusceptible.