The vengeance of God is certain, but certainly not always immediate, nor apparent. The ultimate "vengeance" of God is the denial of the blessings of the Celestial Kingdom, a process brought upon those who will be denied by their own actions and inactions, rather than an emotional vengeance from a loving God. Abinadi is exercising the same poetic license as other prophets who speak against the worldly ways of men.
In this case, the actions of the people will bring these calamities upon themselves, and Abinadi uses them as a sign of the righteousness of God. However, we know that evil frequently goes unpunished in this world, awaiting that final judgment. Dire consequences to not immediately follow evil, and frequently do not follow at all in this lifetime. Were they to do so, it would become rather obvious and uncomfortable to be a sinner, if soon thereafter bad things began to happen. Soon one would understand, as do animals trained in mazes and other experiments, that one should cease to do something that causes distress, even when we might otherwise want to. If such consequences really did come as noticeably as did the calamities upon the remnants of the people of Noah, the process of agency would be short-circuited and become of lessened value.