Will E-Collar training ruin my dog's personality?

No!

Will E-Collar training ruin my dog's personality?

Training is the gateway to a happy and healthy life for your dog. If you have a goofy dog, your dog will still be their goofy self, you will just have a way to communicate to them when it is and isn't appropriate to be goofy. On the other hand, if you have a nervous/timid dog, then training helps them build their confidence and enjoy life much more!