By Pete Jones KINSHASA (Reuters) - The defeat of Democratic Republic of Congo's most important rebel group has strengthened President Joseph Kabila's grip on political power, but bringing peace to his vast central African nation remains a remote prospect. "Thank you, Kabila," sang thousands of women dressed in white who marched through the center of the sprawling riverside capital Kinshasa last week, celebrating the army offensive that routed the M23 rebels in Congo's distant east. A peace deal to be signed on Monday in Entebbe, Uganda, aims to draw a line under the 20-month rebellion, the most serious conflict in Congo since a major war ended in 2003. It caps a dramatic turnaround for the 42-year-old president, whose reputation was in tatters just a year ago, accused by the opposition of rigging a 2011 election and humiliated by M23's capture of Goma, the largest city in eastern Congo.