Hiya OP! The next question you should ask yourself is how much time/effort you’re willing to sink into making him good and erased, smoldering in his shoes; could you live with yourself if you devote a massive amount of time to this, but fail, and something happens to your boyfriend? Or if the target leaves behind an innocent/child relative who commits suicide out of grief due to the loss of this person? I’m not trying to deter you from peeling apart this scum at the molecular level, but I am trying to get you to address the possibilities involved so you screen them for any of the following emotions (aka the “enemy trinity”): doubt, shame, remorse.
When it comes to making good and certain someone is exiled from earth, you have to abandon all other focuses and thoughts. This means you have to convert yourself into an unstoppable force processing reality to attain your objective- you have to murder each and every version of yourself that would feel any shred of doubt, shame, or remorse at obliterating the everloving shit out of someone, or it will kickback to you in some amount. When you’ve completely erased those enemy emotional responses from yourself to any scenario that could involve the target, optionally but optimally any emotional response to them, whatsoever, you’re clear to take aim with certainty the only way your work is getting reversed is by being overpowered.
That being said, even with no skill, there are a few ways to target a system for complete dissolution. The simplest are petitions. It is quite literally just a matter of writing out a letter to an entity as you would a person, either asking them for help or promising some sort of payment upon manifestation of the (extremely specified) end product. Think of it like choosing to ask for a grant, store product, or try to flat out convince them; sometimes even if they aren’t convinced they’ll act, if minimally, to acknowledge your effort. The more you’re willing to put on the line for the manifestation of the end product, the more specific you can predictably be and the more power that will be drawn to respond to your request. In non-worship systems, effort is usually reciprocated with effort, and a low budget way to do this is creativity and craftsmanship.
A less easy way is to hold a funeral for the person, with as much authenticity as you can afford to create but definitely including a burial and acknowledgement of their deeds in life and that a passing on has occurred. You get less specific control, but you entangle them with the initial post-death state, which locks them out of the ability to change their own reality as it slips out of their grasp. Spirits feed on and augment this process.
Last but not least, a cheeky fun way to turn someone into a shitter is found in the Berserk manga. Ever hear of a Brand of Sacrifice? Ritually, in the presence of hungry and powerful shadows and/or during an (most powerfully solar, that you’re physically in the totality of) eclipse, you let the spirits into and through you to channel a sigil onto an enlivened and entangled photo of the target, which thereby dedicates each fabric and quanta of their lives to the spirits of the eclipse, the true demons. This marks them for a fate worse than death! No spoilers though.