public static void handle(key msg, Supplier<NetworkEvent.Context> ctx) {
  if (msg.key == 0 && ctx.get().getSender().getItemStackFromSlot(EquipmentSlotType.FEET)
      .getItem() == ModItems.KABOOTS.get()) {
    ctx.get().enqueueWork(() -> {
      ServerPlayerEntity sender = ctx.get().getSender();
      Vec3d pos = sender.getPositionVec();
      Vec3d look = sender.getLookVec();
      double x = pos.getX() - (look.getX() / 2);
      double y = pos.getY() - 0.3;
      double z = pos.getZ() - (look.getZ() / 2);
      float size = 1.0F;
      sender.world.createExplosion(sender, (DamageSource) null, x, y, z, size, false, Explosion.Mode.BREAK);

      int k1 = MathHelper.floor(x - size - 1.0D);
      int l1 = MathHelper.floor(x + size + 1.0D);
      int i2 = MathHelper.floor(y - size - 1.0D);
      int i1 = MathHelper.floor(y + size + 1.0D);
      int j2 = MathHelper.floor(z - size - 1.0D);
      int j1 = MathHelper.floor(z + size + 1.0D);
      List<Entity> list = sender.getEntityWorld().getEntitiesWithinAABB(LivingEntity.class,
                                                                        new AxisAlignedBB((double) k1, (double) i2, (double) j2, (double) l1, (double) i1, (double) j1),
                                                                        Predicates.instanceOf(LivingEntity.class));
      for (int i = 0; i < list.size(); i++) {
        list.get(i).setVelocity(0, 0, 25);
        CrudeTechMod.log(list.get(i).toString());
      }
    });
  }
  ctx.get().setPacketHandled(true);
}

I am logged, but my velocity doesn't change
 

ServerPlayerEntity['Dev'/50, l='test', x=-299.80, y=3.25, z=433.91]

 

 ctx.get().enqueueWork(() -> {

 

This should be always the first one.

Apparently movement is client-side so that's why it doesn't move me