Faced with utter annihilation, military planners have considered extreme solutions in their quest to stop the Reapers. The two most plausible are the destruction of mass relays and the use of starships as suicide weapons.
Destroying a mass relay to stop the Reapers' advance is infeasible. Although it has recently been proven that mass relays can be destroyed, a ruptured relay liberates enough energy to ruin any terrestrial world in the relay's solar system. It would take too long to evacuate the millions or billions of people living near each relay, and the Council is unwilling to sacrifice that many lives when combat stands a chance of saving them. Even if a garden world were to survive the relay's destruction, the Reapers have infinite patience. They traveled out of dark space using conventional FTL--travel within the galaxy is not an insurmountable barrier.
Meanwhile, starships are too costly to be used as projectiles, given that it would take many collisions to seriously harm a Reaper. Some armchair admirals suggest that a single starship traveling faster than light could obliterate a Reaper capital ship, but all ships based on mass effect technology possess hardwired safety features to prevent FTL collisions. If a ship's FTL plotter finds a significant object in the path of a planned jump, the FTL drive refuses to fire in the first place. This is not a perfect safety feature--the sensors can only scan for objects within a reasonable distance at light speed, and a navigator must plot the rest of the course--but it is so inherent to the FTL warm-up process that removing it is nigh impossible. Cynical intelligence analysts note that the secret of mass effect technology, including that safety system, has always been attributed to the Protheans--just as the mass relays were.