Let me first start off by saying that no monitor (other than possibly a
Varanus komodoensis with a child) is truly aggressive. I have been studying monitors for a number of years in the field, come across them in the field over decades and have had some monster sized (>2.3m) come unknowingly come very close (<2m) to me while I have been in hides. Not once, have I ever had aggression taken against me. To the contrary, they have always put on a display (sometimes hissing or raising the posterior of the body and always throat inflating). They have always moved away from me, with the smaller ones running/diving and the monsters moving away slowly.

(I was just on the other side of the dirt burm from the monitor in the picture)
Monitors are defensive. What makes them appear aggressive is that they are not able to get away- they are trapped. I have a species of monitor that is considered among the most 'aggessive' in captivity,
Varanus bengalensis nebulosus. The male has chased me out of HIS enclosure a number of times. I have been in the field many times with this species- they have always run away, or observed me from a safe distance, high in a tree. If it was a truly aggressive species, it would attack me in its area.
Now, with your next captive monitor, you need to build a relationship with it. This is never going to be done by holding it when it does not want to be held. It has to be left alone and slowly become used to your presence. During this time, you have to give it no reason to make it believe you are a threat.
One of the best analogies that I have heard about doing this, I will now plagiarize: If you want to win the trust of a squirrel in a park, are you going to catch it, grab it and hold it when it does not want to be held? No, you are just going to scare it and it will never trust you. If you offer it food and entice it to come closer and closer over a period of days/weeks and gain its trust by building a relationship with it, it will be coming to you.
Although I have been chased a number of times out of my
Varanus bengalensis nebulosus enclosure by the male, the number of times are rather insignificant considering that I have had the pair for over 40 months, I am able to work in the enclosure with them and have not been bitten once by either of them. An American who came to visit me was shocked that I went to work into the enclosure with shorts and flip flops. He feared them, but I am able to work with them.
Do not ever think that all monitors can be 'tamed'. Each is an individual and there are those that will never trust you and you will never be able to trust them. On the other hand, I have yet to keep a monitor that I can not work with and that I can not 'read' or trust.
Before getting another monitor, please consider this: you are going to be taking on a responsibility that will last for 15-20 years, if you take care of them properly. You already had to give one up. Are you going to be able to take care of another one for 15-20 years (2X the longevity of a dog) even if it turns out to be 'evil'? This is an answer that you should honestly answer to yourself. If the answer is no, please consider another animal