As the greatest sacrifice, a guild leader has to offer happened in "Fairy Tail" 505 where Makarov unleashed The Fairy Law in order to save the future generation of the guild, reports said that this sacrifice would just put in vain as the whole guild will entirely lose hope after Makarov's lost.
As a recap for "Fairy Tail" 505, Zeref is completely destroying the guild that made the protagonists of the manga lose hope. Lady Eileen provided the guild members a secret spell to make them stronger which somehow made their chances to win the battle increase. However, Makarov saw that the spell is not enough and that he has to do something to save the guild and its next generation, so he unleashed the Fairy Law which caused his life.
Fairy Law took effect instantly as Makarov released it, a blast followed Makarov's spell which aided a lot on diminishing the whole army of their enemies. It is hard to decide where Makarov's decision is a good one, since even though "Fairy Tail's" next generation was preserved, the guild lost someone who cares about it more that his life.
On the other hand according to reports, in contrary with the guild leader's death being in vain, Makarov's sacrifice will trigger not the guild to fight their enemies head-on. Additionally, Grey and Natsu will finally understand how they messed up just because of their small, selfish arguments.
Meanwhile, there are also slight chance that Makarov will still be alive and lead the guild to their success against Zeref and the Springgan 12 in the succeeding manga episodes. It can be observed that heroes of "Fairy -Tail" often finds their way out of death-defying mischiefs and situations.
Stay tuned for more of your "Fairy Tail" 506 and other anime updates!