There will be a three-way shootout for qualification from Group H on Tuesday, with Paris St German, Leipzig and the Red Devils all level on nine points heading into the final matchday.
Die Roten Bullen start the evening third in the standings and looking for revenge against section leaders United, who they lost 5-0 to at Old Trafford just six weeks ago.
Leipzig's heaviest-ever European defeat was particularly tough for Angelino given the attack-minded left-back came through the youth ranks at rivals City.
"It was a tough one to take," the 23-year-old Spaniard said. "I think any team that beats you by five goals it's hard to accept, even more when obviously I was at City.
"It was big, big massive game in Manchester and it hurts even more but it's a final for us tomorrow.
"We have to be very focused and be as fresh as possible and hopefully turn everything around so we can forget the last game."
Asked if it would be extra special to knock United out of the Champions League, Angelino said with a laugh: "Of course it's a special game and a special chance but, yeah, we have to do everything that we can to get a good result tomorrow.
"As I said, it's a final. It's either you're in or you're out, so we have to do everything.
"We have to be very focused and hopefully do everything right and so it can be a good night."
Angelino has established himself as an important player with the Bundesliga side, who he re-joined from City in September on a season-long with an option to buy.
"I love it," the Leipzig full-back said. "I love playing football and here they gave me the chance to do it and to express myself every weekend so I'm happy.
"That's why I came here. I wanted to play and they give me minutes, so I'm very happy."
Leipzig will be without Konrad Laimer, Lukas Klostermann and Benjamin Henrichs through injury on Tuesday, while head coach Julian Nagelsmann confirmed teenager Lazar Samardzic has tested positive for Covid-19.
Hwang Hee-chan is unavailable as he recovers from coronavirus and reported United target Dayot Upamecano is suspended for the Group H finale.