  We introduce a novel type of abnormal agents that proceed in the opposite
direction of that defined for the normal agents. A new order parameter, $y$, is
introduced to describe the characteristic of the system. Many interesting
phenomenons emerge as the number of abnormal agents number shifts, e.g., the
system may transform into a new phase (from $y\sim 1$ to $y\sim -1$) suddenly
with abnormal agents getting denser, or stay disordered forever. A variety of
other properties like size effect, agent speed and sight radii that have
impacts on the new collective dynamics are also studied in detail. We suggest
that our model or its modified versions can be applied to explain a variety of
phenomenons with multiple kinds of particles interacting with each other and
shape the system dynamics.
