Short answer: Tiger, Dragon, Snake, Rooster and Ox feel hardest to push
Tiger is direct force. Dragon is presence and command. Snake is unreadable depth. Rooster is sharp standards. Ox is quiet resistance. These signs may feel fierce because they do not easily surrender their boundary.
Tiger is fierce through direct action
Tiger energy reacts quickly when something feels wrong. At its best, it protects, leads and opens a path. Under pressure, especially with too much Fire and not enough cooling Water, it can become impatient.
Dragon, Snake and Rooster create pressure in different ways
Dragon pressure comes from scale, pride and authority. Snake pressure comes from observation and privacy. Rooster pressure comes from accuracy and standards. None of these are bad by default; they become difficult when the chart lacks balance.
Ox is not loud, but it is hard to move
Ox energy can be calm and loyal, but once it has chosen a position, forcing it rarely works. It responds better to time, reasons and practical plans than to emotional pressure.
Fierceness depends on Five Elements
Too much Fire can explode, too much Metal can cut, too much Wood can push, too much Earth can harden, and too much Water can withdraw. A full chart shows whether strong aura becomes protection or pressure.