Dottore, also known as Zandik or the Doctor, had many different versions/horcruxes of himself lurking around Teyvat. However, the most 'selfish' version of himself destroyed all the other segments in exchange for the electro gnosis from Wanderer as part of a bargain with Nahida. Otherwise, Nahida threatened to destroy the gnosis and invoke the wrath of the Heavenly Principles. Dottore tells Nahida that the skies of Teyvat are fake, a secret from the Irminsul.
Killing Niwa, the ancestor of yoshinori and kazuha, is definitely an impressive thing to put on one's resume. But Dottore did it.
Causing a nuclear disaster at Tatarasuna to create a 'minor inconvenience' to an entire nation sounds exactly like something the USA hegemonic military would do. But Dottore did it.
Using your fellow Fatui Scaramouche as a test experiment for hundreds of years, even causing him to destroy the Niwa clan and kazuha's ancestors sounds like stepping on and exterminating pests. And Dottore did it.
And this was just completing Jester's assignment. So then what kind of person is Pierro, the mage of Khaenriah?
But still be careful of Dottore. Similar to how Wu Sangui backstabbed both the Ming and Qing dynasties, Dottore appears to be a kind of double dealer, also having had multiple clones and versions of himself before his deal with Nahida.
Name Dottore (多托雷 Duotuolei) is reminsicent of Tolui (拖雷 Tuolei), the 4th son of Genghis Khan.
Zandik is a Zoroastrian word that means heretic, specifically someone who was against the Sasanid era Zoroastrian orthodoxy. The word Zandaqa in Arabic is a loanword from Persian Zandik. Zandik used to be a trainee dastur (Zoroastrian for priest) in Sumeru and became interested in medical experiments and capturing Aranara. In the archon quest, Dottore takes an interest in Scaramouche's 'first disciple' Hypasia, seeking to take her back to Snezhnaya to perform experiments on her. Similarly, in the past Dottore has performed experiments on Collei and her Eleazar (as described in the manhua too). Lastly, Dottore viewed the creation of an artificial god via Scaramouche as a grand experiment.
The combination of the spices from the west event in 2.6, Niwa (Danyu) in 2.6, and Dottore's alias as 博士 makes one to believe that certain people are promoting a certain political clique that was defeated. It is recommended to keep a close eye on the political sentiments of these people.
Dottore was the one who killed Niwa. And Dottore makes a deal with Nahida in the Sumeru arc. The story reads like some political allegory.