Echo Echo is my favorite alien on Ben 10. His powerful Sonic Blasts can kick enemy away and if he has too many enemy he can self duplicate.  When he scream at ultrasonic frequencies capable of overloading machinery and stopping projectiles in mid-flight. Now Ben has Ultamatrix and Echo Echo become Ultimate Echo Echo on Ben 10 Ultimate Alien. Echo Echo now become blue, green eye,  and look like robot. Sonic Blasts become more powerful skill, Sonic Discs.