What is the ruling on dealing with a colleague who goes too far in joking by hitting and uttering offensive words, knowing that he has shunned me after I responded in kind and he refused my apology?

Harmful joking, whether verbal or physical, is not permissible. Retaliating against a jester's hit with a hit of one's own out of revenge is not justified. Abandoning a Muslim brother for more than three nights due to personal grudges is religiously forbidden, and the better of two disputing parties is the one who initiates the greeting of peace. If the abandonment is from one party only, the sin is upon the abandoner. As for one who seeks forgiveness from someone he wronged, and the wronged person refuses, it is hoped that there will be nothing held against him in the Hereafter, as long as his intention in repentance is sincere.