* Pope's Mass draws huge crowd in Mexico
* Pope denounces drug trafficking, speaks of pain of immigration
* Bishop strongly denounces drug violence
* Benedict leaves for Cuba on Monday (Adds details, background)
By Philip Pullella and Miguel Gutierrez
LEON, Mexico, March 25 (Reuters) - Pope Benedict at a huge outdoor Mass on Sunday condemned drug trafficking and corruption in Mexico, urging people to renounce violence in the country where a brutal war between cartels has killed tens of thousands of people.
On his last day in Mexico, the pope said Mass for a vibrant crowd that organizers estimated at more than 600,000 people in a sprawling park on the edge of Leon, a central city which has escaped the worst of the criminal violence plaguing the country.
Wearing purple and white vestments, the 84-year-old pope addressed the biggest crowd of his Latin American trip from a massive white altar platform on a hillside, sprinkling his sermon with words such as conversion and reconciliation.
Many in the crowd covered their heads with hats, sheets and umbrellas against the blazing sunshine as Benedict prayed that Mexicans would be given the strength "to boldly promote peace, harmony, justice and solidarity."
A spiral of lawlessness has menaced Mexico in the past five years, and many Catholics converging on Leon said they wanted words of hope from the German pontiff.
He said before arriving that he planned to "unmask the evil" of drug trafficking and on Sunday he again addressed the chaos of the turf wars and clashes between drug cartels and the state that have killed more than 50,000 people since 2007.
In his noon prayer, he said Mexicans should look to their faith "at this time when so many families are separated or forced to emigrate, when so many are suffering due to poverty, corruption, domestic violence, drug trafficking, the crisis of values and increased crime."
Benedict also urged them to set aside "futile acts of revenge" and banish all hatred.
Long lines of people, many praying, singing and carrying pictures of the leader of the world's 1.2 billion Roman Catholics and of Our Lady of Guadalupe, Mexico's patron, flooded into the Mass site for hours.
Some camped out for more than a day to get a good spot at the event, the highlight of Benedict's three days in the world's second-most populous Roman Catholic country.
As the pontiff toured the crowd in a "popemobile," he donned a black-and-white sombrero, to the delight of the crowd.
Benedict, who leaves for Cuba on Monday, is making only his second visit to Latin America since his 2005 election. The region is home to about half of the world's Catholics and his predecessor, the late Pope John Paul, visited about once a year.
Benedict reached the Mass on Sunday by helicopter, flying by a giant hilltop monument with the statue of Christ the King, a symbol of the often stormy religious past of Mexico, which was officially anti-clerical for years after a revolution that began in 1910.
The archbishop of Leon, Jose Martin Rabago, set the tone for the day by spelling out the impact of the violence in Mexico.
"In the past few years we have been living through events of violence and death that have generated a painful sensation of fear, helplessness and grief," he said in his welcome address.
Rabago attacked the poverty, lack of opportunity, impunity, injustice and materialism of some Mexicans that he said were the root causes of the country's problems.
"The overwhelming majority of our people," the archbishop told the pope, "does not want to walk along the path of death and destruction. They yearn to live in peace."
Those words brought comfort to Santa Gurrola, a 38-year-old doctor from Zamora in neighboring Michoacan state.
"We are all praying so that our beloved Mexico stops being the place of so many murders. In my state, drug traffickers control everything. We need a blessing from the pope," she said.
President Felipe Calderon has staked his reputation on bringing the drug gangs to heel and the continued violence has eroded support for his conservative National Action Party (PAN), which faces a major struggle to retain the presidency in elections in July.
On Saturday night, the pope comforted a group of eight victims of the drugs war. Joined by Calderon, Benedict met relatives of a soldier and a policeman killed in combat with cartels, a man who survived a kidnapping, and the sister of a student shot by stray bullets during a street fight.
Calderon cannot run for re-election and the PAN's candidate, Josefina Vazquez Mota, trails the presidential front-runner, Enrique Pena Nieto of the opposition Institutional Revolutionary Party (PRI), by double digits in most opinion polls. (Addditional reporting by Mica Rosenberg; Editing by David Brunnstrom and Kieran Murray)