© 2023 MARVEL. MARVEL CONTEST OF CHAMPIONS SOFTWARE © 2023 KABAM GAMES, INC., A NETMARBLE COMPANY. ALL RIGHTS RESERVED.
there are basically 3 types of opponent teams:
-) the normal team: a team owned by another summoner (so there are masteries active) that at least somehow fits to your team's strength
-) the death team: a team owned by another summoner that is VERY hard to beat. it's not impossible, but for the majority of summoners this match up will end your streak.
-) the kang/thanos team: a team owned by AI Kang or Thanos (so there are no masteries active) that is on a "supposed-to-be" level for this arena strengthwise, which means: if you play this arena, this shouldn't be a big problem for you to beat.
usually, you get normal teams from streak 1-5 and you can get them from streak 16 upwards.
kang/thanos teams are usually occuring between streak 6-15, if you match certain criteria... your team should have more than a minimum team rating. how much this minimum team rating is, depends on the streak number (at streak 9 the limit is lower than around streak 11, and it's also lower at 13-15) arena and - as far as i noticed - also increases, when a new highest rank is available (as an example, when the first summoners ranked up their very first 5* rank 5 and 6* rank 2 champs, so the highest possible summoner team rating went up, the minimum team rating for kang/thanos teams went up a bit too).
if you don't meet this minimum team rating between streak 6-15, you will face death teams.
furthermore, there is another minimum team rating between streak 16-21 (but not as high as from 6-15) and a bit lower minimum team rating from streak 21/22 onwards (the exact number of streak is debatable, so better be safe than sorry) that decides between death team or normal team.
for most of the higher arenas, there are strategies & team suggestions how to get past the crucial streaks 6-15/21. i'm afraid there are none for the lower ones... i never saw one for the 2/3* arena, i guess because all the people who are willing to put the time and effort into testing, are already way past this stage of progress or already have so many maxed 2&3* champs, they don't have a problem with death teams in this arena anymore.
i hope this was enlightening and not too complicated. you can find some strategies on youtube and pics of team suggestions for specific arenas via google or some line chats (probably also on other social media channels).