Trynd feels kind of weak in lane, and especially in the jungle. Here is a reasonable buff:

Lets make it so that his crits multiply damaging on hits, but only those which are "always on". Don't confuse on hits with on attacks!

#The following are persistent damaging on hit effects, so they would be multiplied on a crit: 15 magic damage 8% current health damage 15 + 15% AP magic damage Deals up to 60% of attack damage as physical damage to units around target, decaying to 20% near edge Deals 5 + 1% of maximum health to target and 40 + 2.5% of max health as physical damage to other enemies in a cone. 40 magic damage and anything derived from it deals bonus on hit damage to monsters; devourer enchant is 4% max health physical damage

#The following are activated damaging on hits, so they would NOT count at all: and anything derved from it isn't persistent, so the 20 on hit damage isn't multiplied

#The following are damaging on attack effects, so they would NOT be multiplied on a crit: and anything derived from it

#TLDR This change does basically 2 things

• It gives him pretty decent late game AOE with
• gives Trynd a way to handle health stackers with and devourer

This change does NOT

• Improve Tryndamere's early game
• Dramatically improve his damage versus squishies
• Allow him to stick to targets better than he currently does
• Make Tryndamere better specifically against armor stackers
• Magically make him a good team fighter
• Make him any better at taking barons or dragons (damage from botrk and devourer are capped)
• Make him better at finishing off low health targets