New Syntax Fixed!!!

#include <sourcemod>
#include <sdktools>
#include <sdkhooks>

ConVar Enabled;

public Plugin myinfo =  {
    name = "Nade_Kick",
    author = "AgentWesker",
    description = "Player might get his weapon jammed while shooting and he has to reload.",
    version = "0.0.1",
    url = "http://steam-gamers.net"
};

public void OnPluginStart()
{
    //Enabled / Disabled convar
    Enabled = CreateConVar("sm_nadekick_enabled", "1", "Enable/Disable the plugin. Enable = 1.", _, true, 0.0, true, 1.0);

    HookEvent("player_hurt", Event_HandleNadeDamage); //You forgot to make the event hook for player_hurt

    //Execute the config and create if not yet made
    AutoExecConfig(true, "nade_kick");
}

public void OnEntityCreated(int entity, const char[] classname)
{
    //Hook the entity
    SDKHook(entity, SDKHook_SpawnPost, OnEntitySpawned);
}

public void OnEntitySpawned(int entity)
{
    //Is the plugin enabled? Otherwise dont continue
    if (!GetConVarBool(Enabled))
    {
        return;
    }

    char class_name[32];
    GetEdictClassname(entity, class_name, 32);
    int owner = GetEntPropEnt(entity, Prop_Data, "m_hOwnerEntity"); //The client

    //Is the entity a projectile? This ignores weapon spawns
    if (StrContains(class_name, "projectile", false) != -1 && IsValidEntity(entity))
    {
        //Is the projectile an hegrenade?
        if (StrContains(class_name, "hegrenade") != -1)
        {

            //Get the clients angles and position
            float pEyePosition[3], pEyeAngle[3];
            GetClientEyePosition(owner, pEyePosition);
            GetClientEyeAngles(owner, pEyeAngle);

            //To be completed, put these in a hash using client as key

            //Print to chat for debugging purposes
            PrintToChatAll("[SM]%N: My horizontal position is %f %f", owner, pEyePosition[0], pEyePosition[1]);
            PrintToChatAll("[SM]%N: My horizontal angles are %f %f", owner, pEyeAngle[0], pEyeAngle[1]);
        }
    }
}

public void Event_HandleNadeDamage(Event event, const char[] name, bool dontBroadcast) {

    //Get client of attacker and victim
    /*int victimId = GetEventInt(event, "userid")
    int attackerId = GetEventInt(event, "attacker")

    int victim = GetClientOfUserId(victimId);
    int attacker = GetClientOfUserId(attackerId);*/

    //New syntax + easier way to do it
    int victim = GetClientOfUserId(event.GetInt("userid"));
    int attacker = GetClientOfUserId(event.GetInt("attacker"));


    //int damage = GetEventInt(event,"dmg_health");
    int damage = event.GetInt("dmg_health");

    char weapon[32];
    //GetEventString(event, "weapon", weapon, sizeof(weapon));
    event.GetString("weapon", weapon, 32);

    // If the player is a zombie and it is hurt with a grenade
    if (GetClientTeam(victim) == 2 && StrEqual("weapon_hegrenade", weapon, false)) {

        //To be completed, lookup the hash value of the attacker and compare position
        //Also apply attackers directional vector to the grenade
        //Do not apply horizontal vector if the grenade is behind player

        // Generate the vector
        float vector[3];
        vector[0] = 0.0;
        vector[1] = 0.0;
        vector[2] = knockback * damage;

        // Apply the push
        TeleportEntity(victim, NULL_VECTOR, NULL_VECTOR, vector);
    }
}