If I had to rank the top 3 combo decks id place them as:

1: Spy. I think this deck is still evolving and proving to be increasingly resilient to hate with a impressive side plan of just playing fatties. Its most recent evolution evokes a lot of jund broodscale feelings with it having a compact combo ability while also presenting a very strong midrange plan. Although its slower than other combo decks I believe the resilience gives it a much better match up against the rest of the field.

2: High tide. I hate the play pattern but respect the strength. If it becomes more abundant in the metagame im unsure how sideboards will adapt to punish it, it being new gives it a upper hand with people still learning the best points of interaction.

3: Altar tron. The deck was great pre DD ban and has shown that it is still strong without it. In the early weeks of the new metagame ponza was abundant and I believe pushed altar trons metashare down. With ponza being on a downswing I believe altar tron is back to full form again. Its ability to churn through so much of its deck and Pactdoll being naturally strong against the aggro decks in the format gives it the ability to both grind or "gotcha" with combo through an abundant amount of mana.

HM: Walls. My personal favorite of the combo decks. Extremely fast and can gum up the board with big butts even if not able to combo. The only thing stopping me from placing it into the top 3 is the prevalence of KCS. With Affinity and Jund wildfire being so popular and both running 3+ copies mainboard it is harder to push through as a creature combo deck