will a love spell 100% work? no. there are too many variables for any spell to work 100% of the time. love spells do indeed work, but there are many reasons why the may not [or they do but they don't last] what you are asking is to cast over a specific person who [for whatever reason] has left you. he might still have feelings for you and a love spell would manipulate said feelings making him return, but it would not be permanent because his free will would still be there, and if you don't solve the reason why he left in the first place [could be a flaw you can work on, could be he's fallen out of love. again, many options] you're doomed to repeat history and break up. [also, some believe that if a person discovers you cast a love spell on them, they will hate you and no love spell will change that. so there's that risk too]
if i were you i would try a honey jar [since you mentioned how you wish to apologize] and give him space. keep an eye on the situation but don't rush in a beg him to come back. when the time feels right, casually bring it up, say your sorry, and try for a second change. if it's still a no [as hard as it is] accept it and move on.