Garen is basically a weaker version of Renekton

Usually people compare Garen to Darius because they're similar thematically and lore-wise.

But if you look at gameplay Garen is much more similar to Renekton.

Darius is a quintessential Juggernaut, similar to Illaoi, with extreme immobility but the potential to wipe an entire squad if ignored.

Garen and Renekton are both more about closing a gap to a vulnerable target and blowing them up. They're both tanky frontliners with good up-front burst damage and lower DPS. They both have a single-target lockdown and innate tankiness. Other than mastering a simple burst combo on Renekton they pretty much do the same thing but Renekton does it much better.

Garen and Renekton both want to gapclose bot Renekton has a bona fide dash whereas Garen only increases his movespeed.

Garen and Renekton both want to one-shot a target while they're helpless but Renekton gets a stun while Garen only silences, allowing his target to run and autoattack.

Garen and Renekton both have similar burst damage, but Garen's burst takes 3.5s to come out but Renekton gets his burst out in about 1s.

Garen and Renekton both have sustain, but Renekton gets sustain from fighting, whereas Garen only sustains by NOT fighting. This means Renekton can heal by farming but Garen has to watch the minions die if he gets low.

So basically, Renekton is basically like Garen except he gets better mobility, more reliable burst, and better lane sustain. Arguably the only thing Garen does better is his armor shred is more reliable.

While people traditionally say Garen is a weaker version of Darius, in reality, from a gameplay perspective, Garen is a weaker version of Renekton.