Here is the log :

---- Minecraft Crash Report ----
// Sorry

Time: 6/3/17 11:49 AM
Description: Exception in server tick loop

java.lang.OutOfMemoryError: Java heap space
    at java.lang.StringCoding$StringDecoder.decode(Unknown Source)
    at java.lang.StringCoding.decode(Unknown Source)
    at java.lang.String.<init>(Unknown Source)
    at java.util.jar.Manifest.parseName(Unknown Source)
    at java.util.jar.Manifest.read(Unknown Source)
    at java.util.jar.Manifest.<init>(Unknown Source)
    at java.util.jar.JarFile.getManifestFromReference(Unknown Source)
    at java.util.jar.JarFile.getManifest(Unknown Source)
    at sun.misc.URLClassPath$JarLoader$2.getManifest(Unknown Source)
    at java.net.URLClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.access$100(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at org.apache.logging.log4j.core.impl.ThrowableProxy.loadClass(ThrowableProxy.java:459)
    at org.apache.logging.log4j.core.impl.ThrowableProxy.resolvePackageData(ThrowableProxy.java:395)
    at org.apache.logging.log4j.core.impl.ThrowableProxy.<init>(ThrowableProxy.java:97)
    at org.apache.logging.log4j.core.impl.Log4jLogEvent.<init>(Log4jLogEvent.java:114)
    at org.apache.logging.log4j.core.impl.Log4jLogEvent.<init>(Log4jLogEvent.java:90)
    at org.apache.logging.log4j.core.impl.DefaultLogEventFactory.createEvent(DefaultLogEventFactory.java:49)
    at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:365)
    at org.apache.logging.log4j.core.Logger.log(Logger.java:110)
    at org.apache.logging.log4j.spi.AbstractLogger.log(AbstractLogger.java:1448)
    at net.minecraftforge.fml.relauncher.FMLRelaunchLog.log(FMLRelaunchLog.java:92)
    at net.minecraftforge.fml.common.FMLLog.log(FMLLog.java:47)
    at net.minecraftforge.fml.common.LoadController.transition(LoadController.java:167)
    at net.minecraftforge.fml.common.Loader.preinitializeMods(Loader.java:627)
    at net.minecraftforge.fml.server.FMLServerHandler.beginServerLoading(FMLServerHandler.java:99)

A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- System Details --
Details:
    Minecraft Version: 1.10.2
    Operating System: Windows 7 (x86) version 6.1
    Java Version: 1.8.0_131, Oracle Corporation
    Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
    Memory: 485880 bytes (0 MB) / 259522560 bytes (247 MB) up to 259522560 bytes (247 MB)
    JVM Flags: 0 total; 
    IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
    FML: MCP 9.32 Powered by Forge 12.18.3.2297 5 mods loaded, 5 mods active
    States: 'U' = Unloaded 'L' = Loaded 'C' = Constructed 'H' = Pre-initialized 'I' = Initialized 'J' = Post-initialized 'A' = Available 'D' = Disabled 'E' = Errored
    UCH    mcp{9.19} [Minecraft Coder Pack] (minecraft.jar) 
    UCH    FML{8.0.99.99} [Forge Mod Loader] (forge-1.10.2-12.18.3.2297-universal.jar) 
    UCH    Forge{12.18.3.2297} [Minecraft Forge] (forge-1.10.2-12.18.3.2297-universal.jar) 
    UCH    mercurius_updater{1.0} [mercurius_updater] (MercuriusUpdater-1.10.2.jar) 
    UCE    pixelmon{5.0.4} [Pixelmon] (Pixelmon-1.10.2-5.0.4-universal.jar) 
    Loaded coremods (and transformers): 
    Profiler Position: N/A (disabled)
    Is Modded: Definitely; Server brand changed to 'fml,forge'
    Type: Dedicated Server (map_server.txt)

You need to post the fml-client-latest log file, it contains more information than the crash report.

Also, someone else is having issues with pixelmon for 1.10.2, I'd hazard a guess that it's broken and anyone having issues with it should contact the author.

You will unlikely be able to run Pixelmon as it requires about 2Gb to run and you are using 32-bit Java which cannot get more than 1500Mb (ie 1.5Gb), so you will need to install 64-bit Java before trying to assign more RAM