The specific form of safety that a lot of the most-hated champions have is multiple forms of mobility or escape, which allows them to still escape after committing, effectively making them low-risk, high-reward. They generally also have high burst damage, so even when they only make a short in-and-out attack, they still end up taking a large amount of your health bar, often before you can really retaliate.
Well-designed champions with mobility have one single mobility spell, which they can use either to initiate an attack, or to escape. Such champions are almost never hated (unless they are numerically OP), because they have actual risk built into their kits.
For example, Jax jumps onto you, but realises that he will lose the fight (maybe your jungler is just entering the lane) - but once Jax has jumped in, he's committed, he can't just jump back out again (at least for 6 seconds.) Using his mobility offensively gives him a moment of weakness that his enemies can exploit.
For a counter-example: Lee Sin jumps onto you to duel you, but realises that he will lose the fight. He can just drop a ward and Safeguard away, or kick you away from him to abort the fight. It's much harder to make a Lee Sin pay for his mistakes, because he has so many ways to undo them, and this in turn makes playing against him feel unfair and frustrating.
Jump in, ult out
Dash in, pole out
Dash in, return out
Jump in, Safeguard out (or kick away)
Jump in, short CD to jump out (to be fair, she is hated more for being completely uncatchable than because of this)
Jump in, jump or shield-dash out
Dash in, dash out through minions (or block counterattack with his wall)
Swap in, swap out (a small delay before he can do this now.)
Having two dashes on the same champion can still work, though. Look at
. No one complains about his, because it's a fairly slow dash, it can only be used in specific circumstances (has to hit something), it has a very long cooldown, and, most importantly, because Renekton doesn't deal massive burst damage.