1) Certainty 2) Foregone conclusion 3) Sure thing 4) Unavoidability 1) Unavoidability 
ineluctability 1. Not to be avoided, changed, or resisted. 2. Incapable of being evaded; inescapable: 'Death is considered by many to be an ineluctable destiny.'
unavoidability noun the quality of being impossible to avoid or evade