Time delay enemy respawn

With Unity, the most simple script, the better. Miguel and Uriel have good answers, but the most effective way of spawning an enemy Prefab is by having a Spawn Controller. Ill give you an example in Unity Script (you will need 2 scripts: 1.) SpawnController.js (On a new GameObject) 2.) DeathSignal.js (On enemy GameObject)

 //Spawn Controller
 
 var enemy1 : GameObject; //enemy prefab gameobject
 
 var deathTimer = 0; //time since enemy has died.
 var spawnDelay = 5; //spawn delay.
 
 static var isDead = "false";
 
 
 function Update (){
     
    if (isDead == "true"){
         deathTimer += 1 * Time.deltaTime; //start death timer.
 }
    
    if (isDead == "true" && deathTimer == spawnDelay ){
         Spawn(); 
 
 }
 }
 
 function Spawn (){
     Instantiate(enemy1, 0,0,0);
     deathTimer = 0; //reset death timer after spawning.
 }

DeathSignal.js :

      // enemyHealth can be attached to the regular health script
     // by adding enemyHealth = scriptName.Health; in Update function.
     
     var enemy : GameObject;
         
     static var enemyHealth = 100; 
    
             
             function Update(){
                  if (enemyHealth <= 0){  //when enemy health is zero or below Signal Death to Spawn Controller
                      SignalDeath();
             }
             
             }
         
         function SignalDeath (){
             SpawnController.isDead = "true";
             Destroy(enemy);
         }

You could write a small manager script that will spawn this prefab and handle the timing and positions of the spawns.

Like Uriel mentioned, you could call GameObject.Destroy() on it. But if you want your game to run smoothly, destroying and spawning enemies could cost a hefty sum of cpu cycles.

One thing you could do is disable gameObject instead. gameObject.active = false. This disables everything on the object. And when you want to respawn the same kind of prefab again, you could reset the object, position it, and gameObject.active = true.

you have put something simple like this:

Destroy(enemy,1.0);

first you choose the object you want to destroy and then the other the time that he dies.

And you dont want this use the yield WaitForSeconds() but the problem is that you need to check because when you put it at the end(after enemy is death) is different that put it at the begin.