Michael O'Neill's side face Germany in their last group game knowing that a shock victory would send them into the last 16, while a draw would be enough for second spot if Ukraine defeat Poland in the other game.
Magennis accepts that Joachim Low boasts a squad full of quality but says he was brought up to fear "only God" - and vowed to go for the victory.
"After the frustrations of the Poland game, where we knew we could play a lot better in terms of stamping our authority, to play as we did against Ukraine is fantastic," he said.
"A lot of praise has to go to Michael and his backroom staff. At this level, especially with what's at stake, you can't take any liberties. There weren't many of us who deserved to start after the Poland game but everyone who stepped in was fantastic.
"Germany are a dominant force, a possession-based team. They can hurt you from any angle. We know it's going to be tough and we have to take the right decisions at the right time.
"We know they're a very, very good team but every team has its weakness. They have a ridiculous amount of quality but I've been brought up to fear no man, only God.
"We thought before we came to the tournament that we could get through to the last 16. Our mentality is to win games. We had a hard lesson in the first game against Poland but we believe as a group, from the manager to the physios.
"If you don't believe you can win a football match, you're in the wrong sport. We know we won't have 70 per cent of the ball but we're an effective team and we're hard to break down."
After beating Ukraine, Magennis said he would "book a first-class ticket to the moon" if Northern Ireland could follow up with a win over Germany, and the Kilmarnock forward has urged business mogul Richard Branson - whose Virgin company have been developing a commercial space travel programme - to get in touch.
"I tried to get on to Richard Branson but it seems not to be happening," he said. "It's hard to find any more happiness than I was feeling after the game against Ukraine. I couldn't find him, but hopefully he's watching."