Saad Amus is frozen in the cryptobarrios of Bethesda Susa when you find him. If you don't want to fight him, don't wake him up!
If you do want to fight him, note that his jetpack allows him to move almost any distance in a straight line; he will do extremely high damage if he hits you head-on with this movement. Additionally, he has every single sword skill, including normally-incompatible ones, and will use them relentlessly, making him brutally lethal at close range; his sword skills grants him ridiculous accuracy, and his Ceremonial Vibrokhopesh completely ignores AV, so conventional defenses are mostly useless against him. Finally, all his stats are outrageously high; unless you are similarly tough, taking hits from him will usually bring a swift death.
On the other hand, he has no ranged attacks at all, and can therefore be easily beaten by mutants with the Force Wall and / or Force Bubble mutations, provided you can keep them up indefinitely. Additionally, much of his danger comes from his skill with his powerful sword; if you can disarm him, he will be significantly less dangerous. His jetpack-assisted punches will still sting, but probably won't be lethal.
If you can beat him, you can claim his Ceremonial Vibrokhopesh, jeweled sandals, and the Flume-Flier of the Sky-Bear. If you use serrated blade or axes with dismembering you will have a chance to sever Saad Amuses face which will give you +3 ego and -500 reputation with Beasts (this faction is not listed in game) when worn.
Clones of Saad Amus can also sometimes be randomly found in underground tunnels. Like the original, these are contained in cryogenic chambers, and have identical stats and equipment, except they lack the Flume Flier. Unless you want a serious fight, take appropriate caution around them.
It is worth noting that Saad Amus has above average quickness (160) wich combined with the players quickness penalties from being cold allow him to move and attack 2 or 3 times quicker than you.