It would not be the first time that Bayern Munich gets knocked out by a huge underdog. It is 1.5 years ago when Bayern Munich was playing against Villareal and everyone thought that this would be the easiest game ever for the Bavarians. But they lost the first game in the quarterfinals 1-0 and then they tied the second leg although it was a home game. If I had to compare Lazio and Villareal, I would say that they are about similar strength and Bayern should be warned exactly because of the experience they have made with Villareal 
Of course, you have to be careful about this because the team that is not the favorite can cause big difficulties for the team that is the favorite. I think Lazio cannot be considered weak because they performed quite well in the Champions League and they also have some quality players in their team. At least Tuchel must be able to pressure his players to score early to bring down his opponent's mentality. But Bayern Munich are unbeaten in the Champions League this season so I think they are quite consistent in every match they play. Harry Kane is quite dangerous in front of the opponent's goal because he is very good at finding gaps to score goals, so if Lazio is able to stop Harry Kane movements, maybe Lazio will be able to give us a surprise.
Yes I know if we only look at the teams player by player and their standings in the table in the domestic league and then also at their performances thus far in the Champions League group stage, I think the role allocation is obvious for this game. Bayern Munich is by far the favorite to win this round and they are essentially forced to win this round as they have all the pressure, whereas nobody expects Lazio to have a chance and my take is that maybe it is the fact that Lazio is supposed to have no chance, that they actually have a chance. They have nothing to lose when they face Bayern Munich and sometimes that can be quite freeing.