Adon
Birdie
Eagle
Geki
Gen
Lee
Joe
Mike
Retsu
This matchup is pretty balanced, perhaps even slightly in your favor. But it can be difficult at times due to Retsu's great defense and ability to counter your approach. On roundstart, both sides will be looking hard for an opening. Lifelead is very important in this matchup, as both characters have a capable defense against each other. During this stage of the match, be very prudent and cautious. The first hit can decide how the round will go and whether if you'll take the advantage or not.
If you do gain the advantage and a lifelead, then that's great! But don't let your guard down yet, as it's still possible for Retsu to take it back. MP/HP is your best anti air in this matchup, as it beats Retsu's jumpkick cleanly. If Retsu manages to get close to you, LK is great as it knocks him back, does good damage, and beats most of his up-close options.
If you lose lifelead, you may have to take the offensive. Since Retsu's HK can beat out all your moves, you'll need to find an opening where you can hit him or at least trade favorably. MK/HK is probably your most consistent method of approach, as it has good range. Though it can still be beaten out by HK, it's still a safe option if you can time it right.
Jumpkick can be tempting, as its high damage can help you steal rounds, but it's very risky to use. unless done very preemptively, it usually loses to Retsu's jumpkick, and can be easily antiaired by his HK. Neutral jumpkick can be punishing if used recklessly as well, especially if you're within HK range. This doesn't make jumpkick useless, however. If you can catch an opponent off guard and get a successful jumpkick, the round will greatly shift in your favor. Just keep in mind it won't work often.
As Adon does more damage than Retsu, you can generally afford to take more trades in this matchup. The best times to trade are when it'll close the round or guarantee you at least a slight lifelead. Your best move for trades from afar is MK/HK, and up close LK. As long as you don't get beaten out completely, sacrificing a little health to gain the advantage can be worth it.
In summary, keep a close eye on both players' healthbars and prepare to switch from defense to offense depending on the situation. Act cautious and calculated, and you should be able to prevail.
Video of the matchup: https://www.youtube.com/watch?v=ec1EEFfXG2Q
Sagat
Sagat's a powerhouse, but Adon is surprisingly good at dealing with his tools. Use omniblock to dodge tiger shot and MP to block out tiger knee attacks. You're still disadvantaged in this matchup, but at least you can avoid his 2 oppressive tools with good reactions and timing.