I have no idea what con means reading through this profile.
Con : C++ skills for gaming industry
Love : Challenge!
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Pro is Latin for "for"; contra is Latin for "against". Con is simply short for contra (a single syllable to match pro).
For those who want a dictionary, this is OED:
adv. An abbreviation of the Latin prep. contra ‘against’, in the phrase pro-and-con v. (q.v.) ‘for and against’, rarely con and pro.
n. The adv. used as a name for itself; hence, a reason, argument, or arguer against, esp. in pros and cons.
In the context of the CV quoted, it's essentially meaningless. It might mean that he's actually no good at C++, which is unlikely; or it might mean that having used C++ in gaming he's not much use for anything else; or something else.
It's not actually an abbreviation
Look at entries for pros and cons under either pro or con in a dictionary. Where pros are the good things about someone or something, cons are the qualities that get in the way.