23,587 I believe was my best ever damage. Made with the Bronze Axe, Stealthed, with Ninjitsu, and I believe the target was a Warcry or some other low-end mecha.
The pilot survived.
For my mecha, I'm partial to the Savin (special edition especially), the Bargol, and the Ovaknight, though for all three I go with heavy modifications, even before I get innovation (at which point everything that can be upgraded without weight increase, is).
The Savin loses all its (rather useless) installed weapons, batteries, and those installed in its armour (which then have arc thrusters installed), and typically even its leg mounts. Depending on end weight penalties, I might switch out torso armour down to class 6, but I can usually end up with -1/-1/+2 or better with a decent computer + M/T programs.
The Bargol loses its legs (replaced with mountless Savin legs), frequently one of its arms (again, Savin replacements), maybe both if I'm just gunning for a head-cockpit Savin style mecha, and again, any installed weaponry is typically removed wherever possible; I prefer equipped weaponry; this may change if and when the proposed bonus to installed weapons comes in.
The Ovaknight - though I've only managed to grab one once (only time I saw one in a shop and coincidentally happened to have ten million hanging around), also lost those legs in favour of two Savin replacements (four of the legs actually ended up on a lancemate's Savin, would have been two, but I thought that they didn't make "sense" the way they're shaped.
Both the head-mounted mecha usually end up +0/+0/+2 by the time I've finished playing.
With all of them, I also always but always scavenge out the wings of any pixies and put them directly in there, hardened, light and unarmoured wings make for a much improved flight speed. Depending on weight, I also put in two Phoenix backpacks - one Arc 9 and a side mount each, also unarmoured, and typically change their loadouts entirely. By the time I'm done, all three typically get >150 flight/hover/space speeds and
Of them all I'd say the Gladius probably comes out on top when it comes to not-death and general performance.
Hm. Don't think I've ever flown a high end mecha that wasn't massively customised except for a pixie; even then that pixie was probably carrying an Immolation Cannon and a mounted Antique Plasma.