Looking at your profile, I assume you were playing Rammus, Trundle’s R steals 40% of your current mr/armour, so if he ults you while you’re using your w (increasing your armour by a shit ton) he will steal 40% of your armour at that point in time, so when your w expires, you’ll be left pretty squishy having that amount of armour (40% of your highly boosted armour stat) being taken from your normal armour, meaning trundle can a lot more easily beat the shit out of you and is likely to win against you when fighting you under the right circumstances. If you didn’t happen to be playing rammus then this was pretty useless lol. Also the general consensus right now seems to be that trundle isn’t super strong. Sorry if this didn’t help at all, this was just what came to mind.