If the sun became a red giant tomorrow, and Earth found itself inside the outer layers of solar atmosphere, then drag would start slowing it down. In less than 70,000 years, it would fall close enough to the center to be torn apart by tidal forces like one of Saturn’s moons (assuming it hasn’t already been vaporized).

If we’ve already waited 5 billion years to have our revenge, whats another 70k? The lowest amount of Delta V we can spend on this project is zero.