What are the opposite words for lightweight?

When we hear the word "lightweight", we often think of something that is easy to handle because of its lightness. However, there are antonyms for this word, which are heavy, substantial, weighty, and bulky. These antonyms describe things that are dense, hard to lift, or massive. For example, a heavyweight boxer is someone who is significantly heavier than their opponent. A substantial meal is one that leaves you feeling full for hours. Weighty issues require serious consideration and debate. And finally, a bulky piece of furniture takes up a lot of space and is challenging to move. In summary, antonyms for the word "lightweight" describe things that are difficult to move or are physically demanding.