The Adversary
Basics with the ship in Kazon hands finally after teasing us several times over season two, the crew trapped on the planet with no technology as the crew watched the ship leave.
Scorpion
Unimatrix Zero
Shockwave with the Suliban targeting the NX and Archer trapped with Daniels in the devastated 31st century.
The Expanse was less of an OMG cliffhanger but still effective with wanting to know what lies ahead.
Like most arc-based series, ENT's third season had some strong final scene if not necessarily the kind having you on edge but curious what happens next.
Anomaly with Archer walking into the strategy room as the light display falls over his face as the acquired database begins downloading, Rajiin--when things didn't seem like they could get any worse Archer learns a second weapon is being pursued, Rajiin is successfully recaptured with vital biodata and the council is seriously considering going ahead. Exile with the big leap forward by getting its first significant lead on a Xindi colony where part of th weapon is being built.
Stratagem had a nice closing voiceover that really made it feel like they were reaching the end of their journey whether good or bad. Harbinger with the ominous reveal.
Azati Prime was outstanding.
The Council
Countdown
Zero Hour. I know many didn't care for the Alien Nazis but I found it intriguing. Who is the alien? What is going on?
Kir'Shara(which isn't listed)
Babel One and United were both good.