Tamasic action is the most reckless. It is undertaken out of sheer delusion, without pausing to consider four critical things: the consequences it will bring, the losses it will cause, the harm it will inflict on others, and whether one even has the capacity to carry it through.
This is impulse masquerading as action. There is no plan, no foresight, no sense of proportion. A person acting tamasically charges ahead because something inside says 'do it' — not reason, not duty, just a murky compulsion. The damage to oneself and others only becomes visible afterward.
Krishna's list of what the tamasic doer ignores is precise: anubandha (bondage that follows), kshaya (what will be destroyed), hinsa (who will be hurt), and paurusha (whether the task is even within reach). Ignoring all four at once is the signature of tamas.