Hmmm, We've had some scary encounters in the last few years of playing that I'll list below, along w/ one of my first ever sessions from the early 90's.
1. Facing the dragon Perienwyr (sp) in Mercurial seemed like it was going to end our careers early back in SR1 days........
Till we fired multiple AVMs at him.
2. The intro to Extraction from Missions Season 4 w/ the Drones & Sniper & lame set up w/o any prep time was pretty harsh.
3. For that matter the bug nest later that season, #8?, was a nasty bit of business.
4. My GM created some super cyber adepts a while back specifically designed to be nigh unkillable & then tossed them at us 1-3 at a time.
Seriously bouncy w/ boatloads of Armor & Magic Resistance.
5. Just last weekend we were dealing w/ 5 Fully loaded APCs in False Flag all packed w/ Spec Ops Tac Teams.
(AE Loves a full APC, but really those things do NOT like taking damage & shrugged off a LOT of hits)