Hambrabi's melees are like so... I'm shamelessly just translating what little I can from the Japanese wiki here.
Melee Movelist
[5BB] Beam Saber
A 2-part, 4-hit neutral melee attack. Sends the opponent flying away on the 1st hit of the second 5B input. Even for a neutral melee, it does not appear to be very useful, but it really shines as a part of a melee combo. Animation is fairly short, meaning less risk of being cut mid-combo, and the second input can be rainbow stepped into a variety of combo enders. It also has a cancel route into 2B for a combo ender. Done on its own, it does 141 damage.
[8BB] Arm Claw Swipe, Mobile Armor Slash
Hambrabi grinds its claws against the opponent, then transforms into its MA form and does an issen. Holding a direction down during the second B input keeps it in its Mobile Armor form. The animation for this takes a while to complete so it leaves you wide open to being cut and punished by the enemy's partner. Also, the only option for cancelling from this is its csA, limiting its combo potential. Basically its chief use is as a gamble for trying to get out of a sticky situation when your boost gauge is nearly at zero, since Yazan will create some distance between himself and the opponent at the end of the animation. Done on its own, it does 130 damage.
[4/6BB] Two-Saber Stab, Flash Kick
Yazan moves forward while strafing to the side indicated in the input, doing a stab and outward slash with a beam saber in each hand. The combo ender is a Guile-style Somersault Kick. The first part comes out pretty quickly, with good range, and it can stuff other melee approaches. Not as good for attacking an opponent on the retreat. The full combo is a launcher allowing for quite a few followup options (i.e. 4/6BB > AB; 4/6BB > A -> AB; 4/6BB > 8BC > B > AB or 2B). It does the same damage as 8BB on its own--130 damage--but it is quite versatile in comparison.
[2B] Sea Serpent
The obnoxious melee followup mentioned earlier in the thread by vedasisme. Fires a wired anchor at the opponent. On hit, it goes into a throw state where he electrocutes the opposing suit, and then blows them away. You can mash B to add extra damage. His chief melee combo finisher when there's little risk of being cut. Without damage proration, the normal version does 128 damage and the longer version does 164 damage.
[bD B] Drill Attack
Psycho Crusher! The Hambrabi stabs its saber into the opponent and begins to spin to win. Hits 6 times per go. This can be cancelled into itself multiple times, and it takes about 16 hits total to put the opponent into a downed state. If you catch someone off guard with this, you can rack up a decent amount of damage AND create a lot of distance between your opponent and their partner. The common combo ender for this is 2B, but you can follow up with A and AB as well. Without factoring in proration, you get 110 damage from a full spin.
[b while Transformed] Drill Attack
Psycho Crusher (part 2)! Yazan turns around to face the enemy regardless of his heading in MA form and drills right into the gut-area of the enemy MS. Its main uses are for following up 4/6BB to maximize damage output, and mixing up your chase-down options in MA form between it and A. Can be directly cancelled into AB, BC (quick fall), and 2B. Full damage for this (10 hits total) is 141.