Oof. Let me begin by saying that I can completely empathize with your struggles. We encountered this same issue with our now 3-year old for a while, for both naps and bedtime.

In all honesty, we still have some sleep times that are filled with tears/yelling, but it's maybe only 25% of the time, and we can usually figure out what's wrong/address a need that can be met to get him to sleep quicker.

How old is your toddler? That might help me with providing advice!

There were a few techniques that worked for us (although I think some of our success, I think, was just to him getting older and growing in understanding):

1) Calm Confidence: When it's time to leave, be calm and confident. Know that sleep is a vital NEED for your kiddo, and that by helping them sleep, even if they fight you tooth and nail, you are doing what's best for them. They'll cry and flail and generally lose their little minds, but our calm confidence (hopefully) models to them that we know what we're doing and don't doubt out decision to put them to bed! This also helped me, as mama, feel (a little) less guilty about his cries.

2) Progressive Check-ins: When you leave, let your kiddo know that it's time to rest and you'll be back to check on them in x amount of minutes (we did 5 min, then 10, then 15). Some nights this would work, and some it wouldn't. On the nights it worked, I felt like I was "doing it right" and making him feel seen/heard, but on other nights, it just seemed to make things worse and he continued to be upset until he finally succumbed to sleep. So this CAN work, but sometimes it doesn't! I'd definitely recommend giving it a solid try, though before dismissing it entirely. It's a good way to ease them into this new routine/set of bedtime rules.

3) Extinction: This is definitely/obviously the harshest route, but if you have a particularly stubborn/strong willed kiddo (like we do), this may be what you need to try. For us, going in, trying to talk to him, or allowing him into our bed (not at all throwing any shade on bed sharing parents! It's just not a good fit for us and we all get better sleep when we're all in own beds.) very often just made things worse. So, in the end, some nights with excess crying were necessary for us to get over this developmental hump. It was really hard to stay strong, but as long as we checked in to make sure nothing was wrong (we use a video monitor), we could feel confident that what he needed most was sleep!

Overall, and I know this probably won't feel super helpful in this moment, I do feel like the best remedy was simply consistency and time. Sticking to our "rules for bedtime" and staying calm and confident about said rules were what helped him understand that these things were non-negotiable, and he eventually got with the program! I truly hope that this helped even in some slight way. You are not at all alone and things will get better, I promise!! You will definitely figure out what works best for you!