Well this instance of lemmy is very USA centric, so it's definitions of Right Leaning would be a spectrum of Fiscal Conservative to Conservative Religious. That means notable right leaning genocides of the past would include:

15th to 19th Century Indigenous Genocides most recent large scale eradications being the wars against the Cheyenne, Apache, Cherokee, Navajo, and Sioux. While some survivors remain, of the 245 well known original languages there are only fluent speakers in 105 remaining, indicating there are no living members of at least half of the cultures.

35 Million people were brought to the Americas via the African Atlantic Slave Trade, and it's estimated about 20% of them died in transit, which in itself qualifies as a massacre if not genocide.

A lot of genocidal acts took place during the civil war including Fort Pillow Massacre, Lawrence Massacre, Baxter Springs Massacre, etc.

The 1919 Elain Massacre of African Americans in Arkansas.

The 1921 Tulsa Race Massacre is yet another example of racially motivated genocide, it was a hot topic recently as yet another Mass Grave was discovered even while many right leaning individuals refute the existence of the event.

The Phillippine America War saw roughly 220,000 dead natives compared to the 4,200 American deaths.

WWII was basically the only time that an atomic bomb has ever been dropped on a populated city in the world's history, causing an immediate 214,000 deaths, mostly civilian.

In 1995 the Oklahoma City Bombing was instigated by, you'll never guess it, white supremacists. This was the deadliest terrorist attack in modern US history until 9/11.

There were a lot of others both foreign and at home, but for conciseness moving on to Current Examples:

US Right Wing, for example Donald Trump and Desantis, seems to support a Single State Solution of Israel, which is to say complete annihilation of Palestine. In fact, Desantis also wants to defund the United Nations, of all things...

The US owned and operated company Facebook actually facilitated the Rohingya Genocide in Myanmar, something even the state department recognizes as a genocide which is rare.

Many US Right Wing groups want not only a complete isolation from the southern neighbors in Mexico, but an actual military attack on that nation, such as US Senator John Kennedy calling for military intervention.

Some dictatorships created by the USA in the past now still struggle as powerful groups hold very right wing radical opinions and racial prejudices such as Bolivia and Argentina, the former suffering frequent arson and a coup attempt while the latter narrowly electing a far right leader.

Gosh it's actually getting kind of late for me, can somebody else tag in for a while?