The phrase "severely undermined" is grammatically correct and commonly used in written English.
It is typically used to describe a situation or argument that has been significantly weakened or damaged. Example: The scandal severely undermined the politician's credibility and ultimately led to their downfall.
It severely undermined relations between the US and Pakistan.
But his credibility has been severely undermined by the scale of fraud in the first round.
But by introducing such pernicious viruses as Stuxnet and Flame, America has severely undermined its moral and political credibility.
Contraception, no-fault divorce, cohabitation and pornography have already severely undermined the sacred institution of marriage and the family.
Its traditional role as a buffer body between the government and the universities has been severely undermined.
This was a huge issue for players and their agents, because the proposed restrictions could have severely undermined a player's leverage in free agency.
The credibility of Mr. Annan's plan has been severely undermined by the violence, which has left an estimated 10,000 people dead and many more displaced.
Mohamad Ezam Mohamad Nor, from the opposition Keadilan party, points out that Dr Mahathir has severely undermined Malaysia's constitutional checks and balances.
The global financial crisis has severely undermined the economic outlook and recent polls have given a combined majority to the opposition parties.
Shelly Yacimovich, chairwoman of the Labor Party, said he had "severely undermined the rule of law and damaged the public's faith in its elected officials and democracy".
One example is the construction of Israeli settlements in the West Bank and the Gaza Strip, which Secretary Powell said "has severely undermined Palestinian trust and hope".
