After Rwanda essentially cheat-spawned a massive, unopposed army 1,200 miles away from Rwanda itself, it captured (and raped and pillaged) Congo's coastline, oil fields, and main hydroelectric dam. If you ignore the widespread atrocities both sides were now committing (like most of the world did), there weren't any problems ... Until Rwanda's old allies, Angola, Zimbabwe, and Namibia, unexpectedly decided they were fed up with Rwanda's bullshit and switched sides. Angola counter-invaded and recaptured (and re-raped and re-pillaged) the area Kabarebe had taken mere days earlier. Zimbabwe just barely stopped Rwanda from taking the Congo capital at the completely absurd Battle of N'Djili Airport, where Zimbabwean fighter jets had to bomb the other end of the same runway they were taking off from. Namibia's army eventually showed up and got a participation trophy.
Cut off and surrounded by multiple armies, Kabarebe activated his plot armor and teamed up with UNITA to surprise-counter-counter-invade Angola, where his army essentially built their own airport in the jungle and flew away on notorious arms trafficker Viktor Bout's private air force in the middle of the night.
"Operation Kitona" triggered the Second Congo War, AKA "The Great War of Africa," AKA "Africa's World War." Whatever you call it, this massive regional war directly involved a whopping 34 countries and armed groups and killed over 5 million people. It mostly ended in mostly stalemate in 2003, but some fighting continues to this day.