Villas-Boas was the man who signed Lukaku as a 19-year-old from Anderlecht in August 2011 but the Belgium striker did not make his Premier League start until May 2012.
By that point Villas-Boas had been sacked by the Blues and replaced by club legend Roberto Di Matteo, who led Chelsea to a surprise Champions League triumph.
Lukaku, though, had not been registered to play in Europe's premier competition and, although he respected Di Matteo for bringing him along with the rest of the squad for the showdown against Bayern Munich, the now Inter striker still bears a grudge with Villas-Boas.
"Di Matteo told me that I would stay with the group until after the final," Lukaku told Het Laatste Nieuws.
"He thought everyone should come along, including the ones who were suspended and the few boys who were not in the Champions League squad. I am also grateful to him for that.
"This win is one of the things I've always dreamed about. You want to celebrate something like that with the team at that time.
"That is nice in itself at the age of nineteen. I am happy for the whole club, but there is one man who took a lot from me - the previous trainer. I will never forgive him for that."
Lukaku went into more detail about his relationship with Villas-Boas, explaining: "Once I had to play in the front left, another time in the front right. You don't develop that way.
"Then at some point you have to think about yourself. So I told the club what I thought of it. I know Villas-Boas was also under pressure. But that's why he didn't have to treat me like that.
"Di Matteo approached me completely differently, he immediately involved me in everything. That should have been much earlier. Really, I never forgave the previous coach."
While Lukaku was in Munich for Chelsea's Champions League success, he insists he did not even touch the trophy as he did not feel as though he had earned the right.
"I didn't touch it with a finger," he said. "Because I didn't win this trophy myself.
"This has been the case since I was eleven. If I have not contributed anything, it is not my trophy.
"Only if you have contributed to a cup or a title yourself, you can also show it off."