[13:44:46 ERROR]: Encountered an unexpected exception
java.lang.NoClassDefFoundError: org/bukkit/event/player/PlayerAchievementAwardedEvent
        at org.bukkit.command.SimpleCommandMap.setFallbackCommands(SimpleCommandMap.java:78) ~[SimpleCommandMap.class:1.7.10-R0.1-SNAPSHOT]
        at org.bukkit.craftbukkit.v1_7_R4.CraftServer.enablePlugins(CraftServer.java:354) ~[CraftServer.class:1.7.10-R0.1-SNAPSHOT]
        at net.minecraft.server.MinecraftServer.func_71243_i(MinecraftServer.java:511) ~[MinecraftServer.class:?]
        at net.minecr
aft.server.MinecraftServer.func_71222_d(MinecraftServer.java:485) ~[MinecraftServer.class:?]
        at net.minecraft.server.MinecraftServer.func_71247_a(MinecraftServer.java:445) ~[MinecraftServer.class:?]
        at net.minecraft.server.dedicated.DedicatedServer.func_7119
7_b(DedicatedServer.java:336) ~[lt.class:?]
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:631) [MinecraftServer.class:?]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_181]
Caused by: java.lang.ClassNotFoundException: org.bukkit.event.pl
ayer.PlayerAchievementAwardedEvent
        at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191) ~[launchwrapper-1.12.jar:?]
        at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_181]
        at java.lang.ClassLoader.loadClass(Unknow
n Source) ~[?:1.8.0_181]
        ... 8 more
Caused by: java.lang.OutOfMemoryError: GC overhead limit exceeded
[13:44:46 ERROR]:         Cause of unexpected exception was
java.lang.ClassNotFoundException: org.bukkit.event.player.PlayerAchievementAwardedEvent
        at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191) ~[launchwrapper-1.12.jar:?]
        at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_181]
        at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_181]
        at org.bukkit.command.Si

是不是下了高级成就插件？

没有啊，没下过什么高级成就的插件啊

但是你这个好像是插件出问题报错了va.lang.NoClassDefFoundError: org/bukkit/event/player/PlayerAchievementAwardedEvent  achiecementawardedevent看看插件里有这个没有

请检查achiecementawardedevent的版本/配置/前置是否有问题
然后内存多分配一点试试看

此处Out Of Memory表示内存溢出
调高游戏内存可以解决

如果一直都报错，考虑换一个核心文件

换个核心吧