In the Three Kingdoms of Wei, Shu and Wu, the legitimacy of Cao Wei is relatively clear. Although the Cao Wei regime actually seized the Han dynasty by force and failed to truly complete the unification of the Central Plains, the Cao Wei leader Cao Pi established the Wei regime by virtue of the concession of Emperor Xian of the Han Dynasty. In the formal historical process, Cao Pi can be said to act according to the established etiquette and system, so Cao Wei can be considered an orthodox force.
However, from the perspective of orthodoxy alone, perhaps Cao Wei was not necessarily the most righteous force. Because in terms of style, Cao Wei did not take it as his responsibility to support the Han family like Shu Han and win the support of the Han people all over the world. Cao Wei's ruling style relied more on centralization of power, and less consideration for people's livelihood and public opinion, so he may not be regarded as the most righteous force in the eyes of the people.
Compared with Cao Wei and Eastern Wu, Liu Bei's Shu Han can be said to be more upright in his style of acting. Liu Bei has always taken it as his responsibility to help the Han family, and called on the Han people all over the world to work together to eliminate thieves and help the Han. His loyalty and integrity have been widely recognized and supported by the Han people.
After the establishment of the Shu Han regime, Liu Bei also deliberately named it "Shu Han" to demonstrate his determination to support the Han Dynasty. This style of action and the belief of all members have made Shu Han a highly respected force. However, although Shu Han's style of conduct can be called upright, from the perspective of orthodoxy, Shu Han cannot be called an orthodox force. Because Shu Han was not granted by orthodoxy, it was a kind of existence of local separatist forces, and failed to complete unification.
Compared with Cao Wei and Shu Han, the legitimacy of Eastern Wu is also not clear. Sun Quan, the founder of Eastern Wu, was the successor of the state of Wu, but the state of Wu achieved independence in the time of Liu Bei at the cost of abandoning the Han dynasty. Therefore, Soochow also failed to gain the recognition of the orthodox forces, and Soochow did not complete its unification.
It is worth mentioning, however, that Soochow's leadership has ambitions to dominate the world. Sun Quan had launched many foreign conquests, striving to expand the power of Wu and trying to realize his great cause of unification. This ambition for unification and efforts to unify China also gave Soochow a certain influence during the Three Kingdoms period.
To sum up, from the perspective of legitimacy, Cao Wei can be considered the most orthodox force in the Three Kingdoms. Although the way it governs may not be recognized by the people, it has established its power in the system according to the process. Although Shu Han acted in an upright style, it lacked the grant of orthodoxy and could not be regarded as an orthodox force. Although Soochow had the ambition of unification, it also failed to complete the reunification. Therefore, there is no definite answer to who can be considered orthodox among the Three Kingdoms.
When discussing who is orthodox in the Three Kingdoms, we cannot limit ourselves to the identity of the ruler or the name of the regime. More importantly, it is necessary to consider a number of factors, such as their style of conduct, their attitude towards the Han family and the people, and whether or not reunification was completed. Orthodoxy does not come from nominal titles, but is based on institutional legitimacy, popular support, and historical evaluation. During the Three Kingdoms period, each power had its own characteristics and advantages, and orthodoxy was a relative concept, and there was no clear standard. History is like a huge jigsaw puzzle, and each force has given the history of the Three Kingdoms period a variety of colors and meanings.