The only Tier 1 teams in the game are the All-Time teams. Every classic team is Tier 2, and the current teams range from Tiers 3-5. You'll have to beat a Tier 1 team with one of the lower ranked teams. Unfortunately, there's no way to search for a match such that you'll definitely get matched up with a Tier 1 team unless you're playing as a Tier 1 team which won't get you the achievement.
The best bet is to use one of the better Tier 2 teams, like the '87 Lakers or '96 Bulls (as Tier 2 teams are more likely to get matched with a Tier 1 than other teams), and search for a game when not many people are playing. For me, I was playing around 10:30-11 in the morning on a weekday as the '12 Thunder and got matched up with the All-Time Bulls.
Whichever team you end up playing will usually be much better on paper than your team, especially the bench, so try to keep your starters in for as long as possible (make sure to turn auto-substitution off in coach settings before you ready up). There's a lot of luck involved between getting matched up with a higher ranked team, which team you get matched up with and even how good your opponent is. Certain All-Time teams like the the Lakers and Magic are very good and will be tough to beat, with teams like the Timberwolves and Grizzlies being "worse" but still very good. You might be better off going for this achievement while you're still in one of the lower ranked leagues and hope you get matched up with someone who isn't very good. When I played the All-Time Bulls, I was still in JV league and my opponent barely used the Bulls' starters like MJ and Drose, which obviously made it easier.