The phrase "largely opposed to" is correct and usable in written English.
You can use it to indicate that something is mostly, or mostly not, supported or accepted. For example: The mayor was largely opposed to the new tax increase, citing its potential negative effects on the city's citizens.
Christian evangelicals, largely opposed to same-sex marriage, have a large presence in parts of Ohio.
The emphasis, however, is largely opposed to technical display.
Mr. Niccollai said supermarkets were largely opposed to the legislation.
(Republican lawmakers have been largely opposed to swaths of the financial regulation overhaul).
American environmental groups, the national park leadership, Native American groups and local media are largely opposed to the plan.
Arabs are largely opposed to American policies toward Israel and Palestine and to any possible American invasion of Iraq.
Congress and the public have largely been opposed to granting fast-track authority for an agreement that has been negotiated in such secrecy and with so many complicated and controversial issues.
If Clinton runs for president her views on gun control would clash with those of Republicans, who have largely opposed efforts to tighten laws.
America remains a largely conservative country, opposed to gay marriage, worried about crime and suspicious of tax rises.
Crimea was annexed by Russia two years ago, but while many in the peninsula celebrated the event, the Crimean Tatar minority have largely been strongly opposed to Russian rule.
Therefore, construction of power lines in the western Mediterranean Sea is largely possible, as opposed to the great spatial barriers resulting for the eastern Mediterranean Sea in front of the coasts of Egypt and East Libya.
